2.75G is a term occasionally used to refer to EDGE data connectivity, implying that is is faster than GPRS (sometimes called 2.5G), but slower than typical 3G networks. The truth of the matter, however, is that EDGE is an official ITU ratified 3G technology. Typical EDGE implementations generally do not obtain 3G data rates, though, leading people to call it 2.75G.
2.5G
2G