A character's Main Job is the primary job he/she has chosen to use, and which will gain or lose any Experience Points. A Support Job (Subjob) is a secondary job, restricted, if applicable, to half the level of the Main Job, which provides access to additional Job Abilities and Job Traits based upon the restricted level of the subjob.
There are six "Standard Jobs" available to starting characters, and "Advanced Jobs" available to characters that have a Standard job that is at least level thirty and have completed certain quests.
Standard Jobs
Advanced Jobs