The following is a listing of types of star ships, sorted by size.
Small Craft covers one man craft up to ships with a maximum passenger load of about 12.
Midsize Craft include what could be considered large private ships to small capitol ships.
Capitol Ships covers everything else, from Destroyers up through Planet Destroyers.
this ship class ranges widely in size. at its smallest, it is a part of a fighter craft that can be detach in an emergency to carry its pilot to safety. at its largest, they can be the size of a large shuttle to assist the evacuation of large capital ships.
They contain an automatic distress beacon, and the most basic of propulsion systems, as well as life support and food supplies. Their main purpose is to carry surviving crew and pilots away from immediate danger. They are capable of landing on planets, but not of long journeys.
[Notable examples include the one seen in Star Wars (pictured), and the first episode of ST:DS9]
Fighters are designed to be as small and as maneuverable as possible. Their crews are as small as possible, with the primary makeup of the craft being the weapons systems, fuel supplies, engine, and a minimal amount of armor.
Their primary functions for attack and to escort larger ships.
[Examples include Galactica's Colonial Vipers (pictured), B5's Starfurys, and X-wings, Y-wings, TIEs, and Naboo star fighters from Star Wars.]
Bombers serve the same basic function as fighters, only their weapons systems are primarily for ground targets. With a payload of mainly missiles and bombs, it usually requires a larger payload.
[Examples include the TIE Bomber from Star Wars, and select planes in Star Blazers/Yamato.]
Shuttles are primarily used for light transport, of cargo or personnel. Without teleportation technology, shuttles are the primary method of dispatching teams and equipment from ships down to planetary surfaces.
[Examples include the Galileo from Star Trek, the Runabout class ship from ST:DS9, and the shuttlecraft from Battlestar Galactica.]
LACs are essentially fighters that have been equipped with weaponry designed for capital ships. While they are larger and more powerful than fighters, and pack a massive punch for their size, they still have very little protection and are easily destroyed.
[Examples can be found in the Star Fleet Battles game, and the Honor Harrington book series.]
Midsize Craft
The starship equivalent of a tank. Basically a ship is built around a single primary weapon system, with very little extra armor.
[Examples can be found in Star Blazers (Yamato), specifically the ship with the magna flame gun.]
Small trans system ships, built for speed and sometimes luxury.
[Examples can be found in the Honor Harrington book series.]
Of all the ships designed to carry cargo, the freighter is the smallest. Intended for quick cargo runs when speed is more important than quantity. Freighters are also used to ferry cargo off of bulk transports and down to planets/other ships/etc. The freighter is often the vehicle of choice for smugglers.
[Examples include the Millennium Falcon from Star Wars.]
This class of ship has a minimal size crew, with a bulk of the ship being dedicated to sensor equipment, and cargo space for any samples that may be collected during a mission.
[Examples can be found in Babylon 5 and Star Fleet Battles.]
Subs are stealth craft that can hide their appearance, either by hiding under some form of cloaking technology, or by diving into another dimension or subspace. They are designed as either scout craft penetrating deep into enemy territory, or as attack craft mounting surprise attacks, or attacking from hiding.
[Examples can be found in Star Blazers/Yamato season 2 and 3. The Romulan and Klingon Bird of Prey class ships in the Star Trek series.]
Most cultures at least experiment with long range sleeper ships, where the crew takes a long sub light journey in suspended animation so as to be able to survive the duration of the trip. Due to power requirements, and the experimental nature of these flights, such sleeper ships tend to be much smaller than traditional long range or colonization ships... although some sleeper ships are built on a capitol ship scale.
[Examples include the Botany Bay from Star Trek. Other examples can be found in the Alien series, Earth2, and in Galactica.]
Yachts are personal transports... some are modified Freighters, but others are designed specifically for the purpose of personal transportation.
[Examples include the Lady Luck from the Star Wars Novels, and the Captain's Yacht from Star Trek Insurrection.]
Asteroid ships are built out of desperation. They are built from a midsized asteroid that is hollowed out to provide crew and control spaces, and engines are attached to the outside to provide movement. Inspiration for these odd looking, and makeshift ships come from a desire for total secrecy buy building within a chunk of rock, or by shipwrecked crew members who build them as a make-shift life boat. Other situations lend themselves to the development of the Asteroid ship.
[Examples include the prototype sketches of the Yamato, seen in the Yamato comic book, and some of the ships seen in Yamato 2520.]
Destroyers are Light weight combat vessels. They are too lightly armed and armored to act as a stand alone force, however, and normally act in groups or as part of a multi ship convoy. Their primary duties are as escorts for larger ships, or along areas where not much trouble is expected.
[Examples include various Star Wars ships, and ships from the Honor Harrington series, and most of the support EDF Ships in Star Blazers/Yamato, and the Hyperion and similar ships from Babylon 5.]
Cruisers are intended to be the primary workhorse of any mainstream fleet, designed to complete as many different functions as possible. Exploration, courier operations, cargo transport, and even combat operations are possible without excessive alteration of the ship.
[Examples include the Enterprise from Star Trek.]
Medical ships specialize in mass evacuation and treatment of peoples in case of disease plagues or disasters. They also include advanced biological and chemical research labs to perform on site testing and treatment.
Many Medical ships are specially built, but others are modified Frigates or Cruisers.
[Examples include the Pasture from the last episode of ST:TNG, and the Medical Frigate in Star Wars.]
Liners are luxury transports. They are used for vacation tours, casinos, and every other method of relaxing. They are the primary method of civilians to travel between planets.
[Examples include the Rising Star in Galactica, the rebel transport in Star Wars, and the train 999 from Galaxy Express 999.]
Battleships are the ultimate warships, designed to take and dispense punishment. Many a fleet of gunships and destroyers has been obliterated when their fleet commanders miscalculated the amount of damage they could take within the time it would take them to destroy a Battleship.
[Examples include the Yamato from Star Blazers/Yamato, the Arcadia and Queen Emeraldas from Captain Harlock, and the Dreadnought Class from Star Trek or the Star Destroyer class from Star Wars.]
Carriers are also warships, but carry a minimum of offensive or defensive weaponry, relying instead on a fighter screen. The main purpose of the carrier is, of course to carry, and deploy fighters.
[Examples include the Galactica (pictured) and Base Star from Battlestar Galactica, various ships from Star Blazers/Yamato.]
Every ship large enough to be considered a capitol ship (with exceptions) contains at least a small hydroponics area so it can generate oxygen and grow some food for its crew. So ships that specialize in growing food like Agricultural Ships are un-necessary... Except in fleet situations. When lots of ships of various sizes and classes perform long term operations together their food supplies can be very tight, and the Agricultural ships are the result. A single ship that is capable of force-growing enough food to feed an entire fleet of ships.
[Examples include the Agro-ships in Galactica, and the ships in Silent Running.]
Exploration ships are intended to explore and chart deep space, and are also equipped to establish and monitor first contact situations.
[Examples include the Cortez from Babylon 5 other samples can be found in the Star Fleet Battles Game.]
Colony ships are built for the sole purpose of planting a (semi-)self sustaining colony on another world. They carry a minimal crew, colonists, and whatever supplies are expected be needed to get a colony started on a new world. Colony ships are often designed to become part of the colony, and are taken apart and used as building materials, or primary buildings for the first several years of the colony. Some ships are also designed to be able to lift off again to take the colonists back home if a major disaster strikes the colony.
Some Colony ships, in the way they operate, double as other classes of ships... in that some would count as sleeper ships, and most Generational ships are used to place colonies as well.
Most people, instead of judging a ship by size, judge it instead by mass, which in zero gravity gives a better idea of what a ship is capable. So despite the Bulk Cargo Ship's huge size, it has the unloaded mass of a very small ship... a crew of ten would be large. The entire ship is dedicated to propulsion and cargo storage. Lots of cargo storage. The ships loaded mass makes it one of the largest in mass as well as size.
The ship really does nothing but carry large amounts of cargo over large distances.
[Examples can be found in Star Wars novels and computer games, Honor Harrington books, and the Gemini from Galactica.]
Q-ships are either modified Bulk Cargo ships, or are built to look like Bulk Cargo ships... with the main difference being that instead of pulling massive amounts of cargo, they are instead filled with massive amounts of weaponry. They were originally developed as a trap for pirates who hunted the slow moving and lightly armored bulk cargo ships. Depending on the design, they could be either massive warships that can easily match against battleships, or they could be souped up Cargo ships that is really not much better than the ships it is protecting.
[Examples can be found in the Honor Harrington series, and in the game Star Fleet Battles.]
Space stations are more or less stationary space constructions that act as forts, trading posts and repair yards. They normally orbit planets, but they can be placed anywhere really. Larger ones can also act as ship construction yards.
[Examples include Deep Space 9 from ST:DS9, any Starbase from Star Trek, Babylon 5 from B5. Other examples can be found in 2001, the Honor Harrington books, Megazone 23 and Project A-ko.]
Generational ships are a low tech answer to long distance space flights. The ships are built extra large, large enough to simulate a planet surface inside in some cases. the crew and colonists live on the ship, have children, train their children to do their jobs, grow old and die. This process repeats itself several times on the ship until the ship reaches its destination and the however many great grandchildren of the original crew and colonists disembark and establish their colony.
[Examples can be seen on Star Trek, and an old TV movie Earth Star Voyager (?).]
Space colonies are normally started before it is technologically possible to reach other planets. They are essentially larger Space Stations, with many more luxury items. They do have a relatively small crew for their size, and their compliment is much larger than most space stations, except Space Colonies are crewed nearly entirely by civilians.
They have two basic designs a cigar shape, and a ring design. Both generate gravity by rotation, and thus docking bays are kept near the axis of rotation.
[Examples include the sides from the Gundam series. Other examples can be found in the Tom Swift book series, and in the book 2061: Odyssey Three.]
Battle Stations are the ultimate war machines. In essence they are massive mobile space stations that have been ultra fortified and equipped with enough weaponry to take on just about anything. When accompanied by a fleet of support ships, they are nearly invincible.
[Examples include the White Comet, and the Gorba from Star Blazers/Yamato.]
Planet Destroyers are a type of Doomsday Machine, intended as the ultimate threat, which normally only escalate the any given war once they are used. They are a single weapon capable of destroying either an entire planet, or some are even capable of wiping out entire systems by causing suns to go nova. They do include some fighter support and secondary weapons as well for defense, but tend to rely on others for an effective defense.
The one characteristic that all Planet Destroyers seem to share is size. They are big, often the size of a planet itself.
[Examples can be found in the Gal Force trilogy, Babylon 5, and of course include the Death Star, from Star Wars, and the Doomsday Machine from Star Trek.]