It uses cell phone networks to get you on the internet. And it also seems to let you make voice calls. You'll need a data plan on your cellular service to use this.
It is triband GSM which allows you to use it around the world, but will not work with Verizon or Sprint (as they use different techonology)
IIRC, GPRS maxes out at 172kb/s ? But in reality you'll probably get 56kb/s speeds.