http://www.youtube.com/watch?v=jGan8t33Jpw&feature=player_embeddedMultiplayer interview focusing on killstreaks.
I'll sum it up for you:
There are a few different sets of pointstreaks. You earn points by killing and fufiling objectives (planting the bomb for instance.
One way benefits the solo player. It gives you killstreaks like air support and stuff like that.
Another way benefits your team. It gives you killstreaks like recon drones, flak jackets, and stuff that can help you hold an area.
One more way gives you perks. You get an extra perk at 2, 4 and 6, and when you get to 8, you get all of the perks avaliable. (not sure if this means every perk in the game or all the ones you picked.)
Well it's close.