Okay, quick question: Is it Holy Magic in KH or is it Light Magic? And if there's two different versions, what is it?
Light is the "good" force of nature that counters darkness and is Sora and Mickey's main source of power, Holy is a spell that does light damage. The Kingdom Hearts games borrow a lot of elements from Final Fantasy, so a lot of the spells carry over too. It's also known as Pearl or Faith in the games. It appears as either a pillar of light that explodes out of the ground or as homing projectiles.
But for the overall source of power, it's just called The Light.
So it's not necessarily holy magic. It's just light magic?
Well, I suppose you could say they're largely the same thing, but outside of the Hunchback of Notre Dame level in Dream Drop Distance, religion hasn't really been referenced in Kingdom Hearts, so it's a little on the ambiguous side compared to something like Castlevania.