Hope this helps 4G is the 4th generation wireless/mobile network system, which is about 10 times faster than the previous 3G wireless/mobile network system. 4G is also know as LTE (Long Term Evolution) A common point of confusion, is a 3G+ network was also built, which was much faster than 3G and a few carriers referred to 3G+ as 4G, but it's not. I hope that helps, and maybe someone here can explain it better than me.
Simply put, 4G stands for 4th generation. It's the fourth major technology in mobile telecommunications and delivers faster data speeds than the 3G technologies. Confusingly, 4G can refer to two different technologies - WiMax and LTE. In Australia though, it's almost exclusively used to refer to LTE, or what's known as Long Term Evolution. Australia did have a WiMax operator in the form of Vividwireless, right up until the point they were bought out by Optus in early 2012. Optus is now using the spectrum gained through the acquisition to enhance its own LTE network, meaning that WiMax is, for all intends and purposes, obsolete in Australia.