2G 3G 4G - One simple picture!

Cell phones are now world wide, infrastructure for using your phone is not.
I found this image that seems to simplify: "Is your phone 3 or 4 G's?"

So basically all phones are [2G] GSM (for worldwide use);
and newer phones also have [3G] WCDMA and/or [4G] HSPA technology as well.

For more detailed info go here:
http://www.gsmworld.com/technology/index.htm