You can use both EF and EF-S lenses on the body.
EF-S S stands for "short back focus", which means that the rear element of the lens is closer to the image sensor than on regular 35mm, they are made for EOS cameras with APS-C sensors.
EF lenses can be mounted on EF-S bodies but EF-S lenses cannot be mounted on EF bodies.therefore will not fit more expensive pro bodies like the 5D's or 1D's.
If you plan to stick with EOS range then no problem, if you want to progress to pro bodies then think about buying EF lenses.
Buying lenses is expensive and you need to do your homework to make sure you are getting a lens that is going to do what you want, read reviews on-line then always try to go to a shop and ask to try a lens on your body and take a few shots with it.