While (technically) Brig is a name for a ship with a particular arrangement of sails spread across two masts, it was also used as a general term for two masted sailing ships.

Smaller sized sailing vessels that are favoured by independent merchants, as well as navies, pirates and smugglers. While they still need a full sailing crew (20) they are cheaper to buy, and still sail as fast as most other ships. They can carry 100 tons of cargo, and a fair number of seige engines. But there are many different variants.

Navies have well armed vessels, with stronger hulls that carry a complement of marines (Corvettes) and occasional use repurposed merchant vessels (Sloops of War) that have been armed, and may carry marines. Corvettes are used for convoy duty, or long distance patrols, while sloops of war are often used as supply vessels.

Merchants often arm their vessels, and carry a few marines or guards if they are sailing through dangerous, or pirate infested, waters.

The main image is a Corvette, and most merchant vessels look similar. However, you might well come across Dhows or other vessels with similar specifications.