Here's your rating explanation:
Life: Everytime you kill baddies, you get exp, which leads up to a new level every once and a while. When you get a level up, your HP goes up, causing you to live longer
JP:Job points I'm not really sure of, but for instance, I'm a Minstrel, and the higher JP I get, the more songs I can play. Like Heal, Hell Fire, Sleep, Camo, and Focus Energy.
Hunger: This is the little black bar. To replinish hunger, eat avocados so you don't die from starvation, which is located at the Jova mart.