hi, i want to get a handheld console soon,still cant decide PSP or NDSL, but that not the point here

i never play/touch a psp before, i want to ask, do i need to pay to play multiplater game with psp?
or do i need anything extra to play multiplayer game.
i read a few thread and i found something about KAI and ad-hoc game, what is that?

sorry guys... noob here