twerppoet
iPad Fan
If you head on over to the Hacking forum on this site there are a couple of sticky (always at the top of the list) threads about jailbreaking whys, hows, and whats. That would answer your questions faster than I can here. Besides, I don't know much myself. There are good reasons for jailbreaking, but none of them apply to me at the moment so I haven't dug into the details.