Hi, I am looking into making a video game involved with using and building ships like those of 16th - 18th century. What I need to clarify is how it was decided what would a new ship be called? if classifications like galeona, caravella, frigate etc. were decided only by the intended purpose of the ship or was it by the specific features, designs or something tangible? Thank you.
First, sailing vessels should not be referred to as "ships." A ship is a sailing vessel with sails and masts that are ship-rigged, 3 or more masts with square sails with the mizzen mast rigged with a lower mizzen sail. A closely rigged vessel to that of a ship would be a barque which has 3 or more masts with square sails, but the mizzen mast is fully rigged with fore-and-aft sails.
Sail and mast layout is an important part in the classification of a vessel. A schooner will have 2 or more masts all rigged with fore-and-aft sails. A Snow is a 2 mast, square sail rigged vessel with a snow-mast/trysail-mast behind the mainmast. A tartane had a mainmast with a lateen sail with small square topsail and raffee sails. A Xebec had 3 masts rigged with lateen sails. There are tons of other vessels/rigging/layouts that make each vessel unique.
Next, for men-of-war the classification has to do with number of guns, rigging/mast layout, and number of gun decks.
Looking at the British Royal Navy in the late 18th century you have these classifications:
Ships of the line
First Rate: 100+ guns, three gun decks, 3 masts ship-rigged.
Second Rate: 90+ guns, three gun decks, 3 masts ship-rigged.
Third Rate: 64-80+ guns, two gun decks, 3 masts ship-rigged.
Fourth Rate: 50+ guns, two gun decks, 3 masts ship-rigged.
Frigates
Fifth Rate: 32-44+ guns, one gun deck, 3 masts ship-rigged. This classification can include razeed 3rd/4th rates. By cutting off the upper deck rate it was turned into a "heavy" frigate, it still mounted the larger guns of a ship of the line, but gained the speed and maneuverability of a frigate.
Sixth Rate: 24+ guns, one gun deck, 3 masts ship-rigged. Sometimes called a "jackass" frigate due to its small size and number of guns.
Post Ships: 20+ guns, one gun deck, 3 masts ship-rigged. Not a frigate, but still a rated ship which had to be commanded by a Post Captain.
Sloop-of-War
2 or 3 masts depending on time period. Less than 20 guns on one gun deck. Could be rigged in a variety of ways: ship-rigged, brig-rigged, Bermuda, etc. Captained by a Master and Commander/Commander.
Brig
2 masts, brig-rigged with square sails. Less than 20 guns. Greatly varied in size, brigs could be captained by commanders or lieutenants depending on size/number of guns.
Hope this helps.
I've answered some previous questions about this that may be of interest to you:
https://www.reddit.com/r/AskHistorians/comments/1lmtd5/what_advances_in_naval_technology_were_made/
https://www.reddit.com/r/AskHistorians/comments/20x9kz/classes_of_vessels_during_the_age_of_sail/
https://www.reddit.com/r/AskHistorians/comments/2fs8qr/how_much_more_advanced_was_a_british/
Something to keep in mind is that the classifications of vessels you mention are somewhat read back into history -- I understand the mechanics of why would be useful in a game setting to have a class of ships that you unlock by ________, and it makes sense to group ships together; but, in the historical moment the distinction between say a caravel and a galleon wasn't always immediately clear-cut and there was an evolution over time.
That said, how we classify ships is definitely based on their intended purpose, which influences the features/designs. That is to say, a ship's features/designs are defined when it's being designed, based on what its role needs to be. The comment elsewhere from /u/Colonel-Gentleman is important for understanding broad classifications, but it was initially set by the Admiralty of the late 17th century to plan for how many guns a ship would carry and thus how many men, and it's less descriptive of a class of ship than it's often used to be.
Anyhow, take a look through those other comments and if you have a follow-up please do let me know!
Thanks to all of you for your input. I will read through what you presented to me.