you can do anything to a jpeg that you can can do to a raw file, the difference is just that the end result will be better with a raw file.
Jpeg files are compressed, which means some of the data is lost and the file size is smaller than the uncompressed, all data raw file. The upside to jpeg is that it will fit more of them on a memory card and they are written faster (as they are smaller), but the downside is you have less data to work with if you're trying to post process the file, giving you a lower quality end result. This is more true the farther away from pristine the picture is when captured..