"EDGE is a wireless network technology generally considered the next step in the 2G network. The name is an acronym that stands for Enhanced Data GSM Environment. Enhanced Data Rates for GSM Evolution is an alternative name that is also used. As both names suggest, EDGE is an improvement on the GSM wireless technology, which is second generation, or 2G, cell phone technology. Since EDGE is an improvement on existing technology and not necessarily a third generation, it is often referred to as 2.75G."
http://www.wisegeek.com/what-is-edge.htm
"EDGE is used automatically when both the phone and network support it. EDGE phones will automatically revert to the slower GPRS standard when EDGE service is not available.
Although many EDGE phones and devices are theoretically capable of up to 236 Kbps, most EDGE networks are only configured to allow up to 135 Kbps, to conserve spectrum resources. Real-world data rates are usually lower than the maximum.
Because it is based on existing GSM and GPRS technology, EDGE is a smooth upgrade for GSM network operators.
Although EDGE works at a low level within the GSM standard that includes voice, the main benefit is to increase GPRS data rates. GPRS operating over EDGE is called EGPRS.
Although EDGE is faster than GPRS, it is not as fast as 3G technologies such as HSDPA and EVDO."
http://www.phonescoop.com.com/glossary/term.php?gid=107