A Cannon is a large gun used to fire various forms of projectiles at an enemy. On-board British ships cannon took two forms, the long gun and the carronade. Both forms of cannon used gunpowder (black powder) and the projectiles took many forms such as round shot, barshot, grapeshot, canister, and others.
A long gun was designed for range, 9pdrs were often of this form and called 'long nines'
A carronade was shorter, and while it had shorter range, it was lighter and was popular for the close combat the Royal Navy preferred.
A tampion is a plug kept in the muzzle of a cannon to keep out weather when the cannon is not in use.