What is Defense up and Offense up?

Many characters give defense up/down or offense up/down, but there is no character Stat "defense" or "offense", so how am I supposed to know how these abilities affect my team or whether I want to use them? Can we make this more transparent please??

Or can we view stats live in-game to view how they change when these spells are in play?

Or can we get a training arena where we can view how these buffs/debuffs change our teams?