3G stands for 3rd generation and 4G stands for 4th generation.The difference between them is that 3G is 3G speeds are slower than 4G and 3G can reach up to 3 megabits per second.At 3G speed it can download roughly 1 to 2 minites to download 4 minute mp3 file.4G is faster and are trying to get up to 100 megabits per second to 1 gigabit per second an is 10 to 100 times better then 3G and can download a 4 minute mp3 download file a few seconds rather than the 1 to 2 minutes on 3G.
Sprint is the only true 4G service that has 2 4G phones now the HTC Evo and the Samsung Epic.
By Liz Patt
http://mylifescoop.com/featured-stories/2011/02/whats-the-difference-between-3g-and-4g.html