What is 4G?
"What is 4G I keep hearing everyone talking about?"
4G is the popular name for the latest generation of cell phone data and voice services. The previous generation (widely available from all carriers) was called 3G. What makes 4G different from 3G is the ability to handle a far greater capacity of both voice and data traffic. If you've ever been to a large venue, like a sporting event or outdoor concert, and found yourself unable to place a call or get your email because the network was busy, you will appreciate the significance of this. With 4G you shouldn't see the same kinds of overcapacity issues.
As of this writing, Sprint is currently the only 4G cell phone and cellular data provider through a partnership with Clearwire. The combination of the two companies provide 3G cellular data service in places where 4G isn't available, while offering the higher capacity 4G service through devices like the Sprint Overdrive and cellphones like the Samsung Epic (Galaxy S) as well as the HTC Evo. Sprint currently boasts download speeds of up to 10 megabits per second using their 4G devices, but I haven't actually seen that in practice with my own 4G Sprint Overdrive device.
Verizon is joining the 4G party with the competing Verizon LTE offering. LTE is believed to be somewhere in the 5 - 12 megabits per second range for downloads.
You can hear about some of the benefits of 4G in this interview I did with a Sprint representative.