Answer:
If you mean the difference it's quit alot. The iPhone 4 includes a retina screen, a new design and style, it shoots HD videos and pictures and it has flash. It almost the same as the iPhone 3GS because you can shoot video and edit it and you can still send video messages. Oh and the iPhone 4 has facetalk (one camera in the back and one i the front) as the 3GS only has one in the back.
hope this helped !
:D