EDGE Falls under 2.5G, not 3rd Generation when talked to by most people.
3G is a network type, EDGE gives some benefits of 3G but its running on a 2G network; thus it's generaly 2.5G. You can call it 3G for its data transfer rate but you're not really running on a 3rd generation network.
for more info on 3G & http://en.wikipedia.org/wiki/2.5G
for info on 2.5G; Yes I know wikipedia isn't always the best source for information, but it was the quickest thing at the moment.
Edit: Added 2.5G Link.