centrino means you can connect wirelessly to a nearby wireless access point. e.g. if you have broadband through a gateway, chances are you will be able to access it through your laptop when you set it up. you can't use it anywhere, the range is limited. in my house it works for about 50m, but the access point doesn't give a very strong signal, so even though i have centrino, i had to buy a PCMCIA wireless network card to get the net in my room and boost the signal. otherwise buy a stronger access point, which is a lot more expensive.
the companies that have wireless pc modems will allow you to access the internet almost anywhere e.g. iburst. you have to plug the modem in and take it with you.
if you're at uni, like unsw and usyd have wireless networks, so you can access the net there through a laptop with centrino or wireless. sometimes across sydney you can gain access to unsecured networks that other people have left open, but you're not supposed to do that.
ummm i can't explain bluetooth... only know the wireless stuff through months of trying to get mine to work in the stupid house properly.
oh and someone correct me or tell me if i'm wrong about anything, this is just what i've picked up, i'm not a very techy person.
