A cannon was a large firearm commonly used by ships and forts. This artillery weapon was the main defensive/offensive weapon on ships, although boarding other vessels was also common, as well as on battlefields all over the world.
Primitive cannons date back as early as 200 BC, but battlefield use was first reported on January 28, 1132. The weapon was used during the Hundred Years War, as well as aboard ships as early as 1250. By 1380, cannons mounted on wheels had been deployed.
Once the middle ages ended, cannons became larger and larger and more common than ever before. They made weapons such as siege towers and the like obsolete and castles less important. Forts started featuring cannon batteries as a main defense during the Renaissance. Cannons are defined by their pound rating (the weight of a single solid iron shot fired by that bore of cannon); common types ranged from 42-pounders, 32-pounders, 24-pounders, 18-pounders, 12-pounders, 9-pounders, 8-pounders, 6-pounders, and various smaller calibers.
Both merchant ships like the Edinburgh Trader as well as pirate ships like the Black Pearl and small Navy ships like the HMS Interceptor carried relatively light 6- and 4-pounders while big warships and forts normally carried much larger guns.
Normally, a cannon was crewed by five men, but in case of a lack of crewmen, they could be handled by a smaller crew of two or three gunners.  Normally, the cannons on a ship are located behind gunports on the sides, so the ship can only fire broadsides, but some ships posseses bow– or stern chasers which allow them to fire in all directions.
Merchant ships used their cannons to combat against pirate attacks, and British Royal Navy and East India Trading Company ships often sunk hostile ships by gunfire. Pirates normally only tried to damage their victims in order to facilitate boarding, as their intention was to pilfer the ships and not to sink them. The same tactic was sometimes used by the Navy and the East India Trading Company.