What is the difference in 3G and 4G?

Like I know that they are generations and all. But like I don't understand. I have the iPhone 4 and at the top on my screen it says 3G? I would figure since I have the iPhone 4 that it should be 4G but it says 3G so someone please explain to me what they mean.

4G is faster

The difference is 3G is fast but it is slower it has less data and 4G is so called faster I think they are pretty much the same

1: 4g is slightly faster not a huge difference but noticeable 2: try updating your phone by connecting to iTunes it should switch it to 4g

This are data speeds. IPhone 4 was release during the time where 3rd generation data speeds where only available(3G). Updating or doing anything to it will not give you 4G speeds. This is something that needs to be implemented when the phone is made. 4G is much faster Internet much like if you were connected to Wi-Fi. It is also called LTE. Only the new iPhone 5 supports 4G.