"Ce" means "this/that" as in "this boy " or "this/that  month" . You would say "ce garçon" or "ce mois."  This is a demonstrative pronoun, pointing out which one you're talking about -- that one.

The "this" or "that" represented by "ça" is more of a standalone "this/that."

I know that : "Je sais ça."        I'm using that!   "J'utilise ça!"