In Tales you find yourself moving through a variety of scenarios, with a progressing story of up to 20 levels.  As you progress through you will level up, which will unlock new abilities that you can bring into each battle, and eventually turn into even stronger abilities, and of course you will find gear to buff up even more as you go.   Each of these abilities operates on either a cooldown (ie x rounds until you can use it again) or it has a number of charges and once they are used you are out for the rest of that mission