Yes, but you will need a xbox360 live gold membership card to be able to play them online.
No. The networks are separate.
Yes, in fact you can play with 4 players in some games. You can play up to 16 online.
Well, and Xbox360/Xbox lets you connect, and play against your friends online. And you can still have fun in Campaign in some Xbox360/Xbox games to.
There is upsides to both, the xbox has more games on it, the ps3 has free online but less games to Play.
A Xbox360 is a console, the second after the first Xbox. You play Xbox360 games on it and I think you can download or buy a thing so you can play your Xbox games on it to.
No there are not any halo games available to play online. All halo games are in disk form, available on ps2, Xbox, xbox360. Sorry this was no help to you.
No.
no
no, you only need xbox live if you want to play online
Yes you can.
no it is not possable