In Pirate101, there are 5 classes. They are listed below with the links to pages with much better information on them.
Swashbuckler Uses speed and finesse in battle.
Buccaneer- Uses Brute strength to force their enemies into submission.
Witchdoctor- Uses Voodoo magic to attack enemies and strengthen allies.
Privateer- Are tough in battle, and also can heal and inspire their allies in battle.
Musketeer- Use long range weapons and set traps in battle.