Level is a measure of how experienced a character is. Level is used to calculate the amount of damage done by an attack, often in conjunction with Weapon Power. Every time a player character increases in level, the amount of Health they have is increased by one, as well as the amount of Ether they have, if the character is of a job class that uses Ether.
Level increases after each victorious battle, going up by one full level until level 10, by half of one level until level 20, by one third of one level until level 30, by one quarter of one level until level 40, and by one fifth of one level thereafter. This rate may be increased by artifact such as the Medal of Glory. Level can also be increased by consumable items such as Level Up Mushrooms, or at the Quest Master's discretion.
Achieving certain levels also unlocks more job class options, with the Advanced Classes becoming available at level 15, the Expert Classes at level 30, the Veteran Classes at level 40, and the Master Classes at level 50. Second characters are also unlocked at level 50.