patch 1.21, players in Final Fantasy XIV will have a new way to improve their characters. Leveling a class won't be changing, but the job system will allow characters to reach the full potential of a given discipline. The latest preview goes into depth about the process of unlocking and improving each of the new jobs, with each job requiring a primary class at level 30 and a supplementary class at level 15.
Once a job is unlocked, players can equip the job's Soul Crystal to switch to the specific job. This will allow the player access to job-specific skills, but it will also carry limitations -- players will be limited in the number of actions that can be equipped from other classes, and they can only use actions from specific classes. If you're more of the crafty sort, of course, you won't be getting in on the new jobs, but you will be able to take advantage of the newly streamlined recipes for accessories, food, and medicines. So there's a little something for everyone.