Mana Points

Mana Points (or referred to as MP, Mana) is energy that is used to cast your Special Attacks your Character's Job has. It is the blue bar at the bottom of the screen next to the Health Points Bar.

When the MP Bar reaches 0 or gets too low, your character cannot activate any more of his/her skills until you either wait for it to regain itself slowly, or use a Mana Potion.