What does "CDMA" mean?
Canadian Donkey and Mule Association
For phone voice & data standards, just Wiki it:
http://en.wikipedia.org/wiki/List_of_mobile_phone_standards
The iPhone is Quad band GSM (850/900/1800/1900 MHz). It will work everywhere in the world. GSM is what the rest of the world is using. I'd like to remind everyone here, the US is NOT the leader in mobile telephony. It is happening in China and India where people will gladly shell out $500-$750 for a mobile phone because its the in-thing to do and over 8 million new subscribers are added EVERY month. Nokia and Samsung are the leading companies.
What is really bad about AT&T (formerly Cingular) is that they will NOT unlock your phone so that it can be used with another carrier. Lets say you have an unlocked iPhone, then you can use it with any GSM carrier in the world. If its locked to AT&T, then you can't unlock it and you're stuck if you wish to change carriers. Additionally, if the next gen of iPhone comes out in a couple of years, you can only sell your iPhone to another AT&T customer. Its a bad deal.
I recommend people to stay away from AT&T. If Apple doesn't agressively market the iPhone in Asia, they will ultimately find that it isn't a profitable product. The mobile phone industry is much more different than portable music player concept.