bryann80 is right. Let me add, though, that the origin of Hallelujah is religious. It is an old hebrew exclamation that means 'praise God!' It's used as such eg in the christian worship service. In a more secular context though, it means exactly what bryann explained.

Hallelouya is an esclamation to say that a a thing has gone all right, so you're happy and say at the sky HALLELOUYAAAA!!! You can say yu huuuuu or..... YATTA in japan for example :). I don't kno if I was clear :P