Newbie needs glossary

[Londo13]

I’m new to this ‘sport’ and need a little help understanding some of the terms. For the past month, I have reflashed my XV6700 with about 4 different rom images and played with the registry. It been interesting to say the least. But I can’t seem to find the definitions for these terms and how they relate to the 2 bands, ie. 800 and 1900.
What does 1xRTT, CDMA, EV-DO, and GSM, represent? Thanks