The job center allows you to pick a job to improve your character. There are currently 3 jobs available at Refaim, warrior, merchant and scholar. The Warrior job focuses on improving strength by defeating creatures. The Merchant job focuses on the ability to make money by selling things to the Hoarder. The Scholar job focuses on gaining wisdom by reading books. Each of these jobs have their own benefits and once you start one you cannot switch without starting over, so pick the one that fits you most.