What it means by 1G, 2G, 3G and 4G is that they are the generation of radio technology. The 4G is better because it can let you access internet further and faster than 3G does. The new generation called 4G is 10x faster than 3G but if you want a 4G as your service there's going to be a $10 premium fee that you have to pay monthly. The Sprint is the only carriers that offers 4G but soon other carriers like T-mobile, AT&T, and Verizon is going to offer 4G. The 4G can speed up to 100 Mbps which is really fast it could download music in a second which is pretty amazing.
http://mylifescoop.com/featured-stories/2011/02/whats-the-difference-between-3g-and-4g.html
By Liz Patt