3G is part of the cellular network in the US. The Nook WIFI/3G will try to connect to wifi networks first and then look for the 3G cellular signal by AT&T next. Once the download is complete the Nook will disconnect from either one automatically.
Download books in seconds.
Wi-Fi ( 802.11 b/g).
Free Wi-Fi in all Barnes & Noble stores.
Free Wi-Fi in all AT&T hotspots
NOOK 3G+Wi-Fi includes FREE wireless connectivity via AT&T, the nation's fastest 3G network - with no fees or contracts. *
Available now in over 190 U.S. cities, AT&T 3G Wireless service provides accelerated data speeds and data capabilities for an amazing wireless data experience.
Disclaimer: 3G network not available in all areas