Jobs are a way to allow your character to specialize in a certain area, such as magic or melee at its most basic level, and add another layer to the complexity of forming team synergy and strategy. All of the jobs are naturally unlocked as you progress through the game. Each Crystal you restore will add to your job list, so you don’t need to worry about going out of your way for all of them (except the Onion Knight job, which is in no way necessary for game completion).
Different jobs can equip different weapons. Knights, for instance, can equip swords , but not a bow and arrow, which a Ranger can use. Many magic classes also can only use very specific pieces of armor, and some other classes, such as Thieves and Monks, have other specialized armors just for them.
There are a total of 23 jobs in FFIII. One of them, the Freelancer, is the initial job you get when you first start the game. The last one, the Onion Knight job, is exclusive to a sidequest. DS users will need to have the data from Wi-Fi downloads that are no longer available (sorry new players), whereas Steam users merely need to have certain percent benchmarks completed in their Bestiary.
This section will provide you with everything you need to know about all jobs, including the Onion Knight. Bear in mind that though some jobs are more favored over others, all are equally useable. If you find yourself liking a job and worry that it isn’t very good, don’t worry. In only a few instances are some jobs strict upgrades, and they will be pointed out to you.