Hi,
Bluetooths original purpose in life was to replace cables between devices. Suchs as between headsets and phones.
Its intended to be short distance and is not very fast. (750kbps ish)
WiFi comes in various flavours, most common is known as 802.11b and works at around 11Mbps, purpose to replace wired networks. Increasingly you will meet 802.11g which works ar around 54Mbps (in reality nearer 22Mbps).
Bluetooth and WiFi do operate around the same part of the frequency spectrum so can interfere, in practice Ive not had any problems myself but its worth knowing.
We mustnt forget good old reliable InfraRed, (aka IrDA), which uses light instead of radio frequency. Speeds up to around 16Mbps possible, but most commonly PDAs are 4mbps or most common 115Kbps. For a definitive explanation of flavours of infra red
see
http://www.irda.orgIrDA and Bluetooth are somewhat similar in the use but each has advantages in different situtations
Theres a good article comparing Bluetooth and IrDA at
http://www.dpi.net.ir/pc/MobileComputing/articles/IrDA%20versus%20Bluetooth%20A%20Complementary%20Comparison.htmAny of the above can be used to get internet access. I frequently use infra-red and bluetooth to connect to the internet using my phone and also via my desktop pc. Your internet enabled applications, mail/browsers/ftp etc dont care how the physical connection is made, so what works over one method eg WiFi should willl work over irDa/Bluetooth/Serial or whatever. (though some phones can be a bit weird and some networks restrict some services)
Out and about you are more likley to find WiFi access points in train stations, coffee shops etc.
For a more coherent and articulate comparison and explanation than mine take a look at
http://www.thetravelinsider.info/roadwarriorcontent/bluetooth.htmI hope some of this helps....
best wishes
Jon.T
ps is there anyone else here?