3G stands for third generation mobile telecommunications, and 4G stands for fourth generation mobile telecommunications. 3G devices allow faster and safer data transfer. This makes it easier to access the Internet. 4G is an even more improved system that can download speeds of 100 megabytes per second while in motion. (1 gigabyte while stationary.) It has high sound quality and exceptionally fast Internet connection, and data transfer. There are a lot of arguments concerning what 4G really can or cannot do, and if it even works. Carrier companies who offer 4G are Sprint, Verizon Wireless, and T-Mobile. Carriers who say they offer 4G but don't are AT&T Networks.
Sources: http://www.howitworksdaily.com/technology/whats-the-difference-between-3g-and-4g/
Author: Darren Pearlman
http://www.cnn.com/2011/11/01/tech/mobile/consumers-covet-4g-wired/index.html
Author: Christina Bonnington