3G is the wireless network standard used in the iPhone 3G. It is called 3G because it is the third generation of cellular telecom standards.
EDGE: 1 Mbit/s download and 400 kbit/s upload
3G: 14.4 Mbit/s down and 5.8 Mbit/s up.
3G’s ability to handle more data makes it faster, but also improves the phone call sound quality.
Support for 3G in the iPhone 3G is generally seen as a factor that contributes to faster drain of the phone’s battery.