Just to clarify a little. 🙂
You CAN use an EF lens on EF-S (a crop-sensor APS-C camera), but you CAN’T use an EF-S on a full frame EF mount camera.
That’s nice, because you can invest in expensive, good glass that is still compatible with your cheaper camera, then when you upgrade to a full frame camera, you still get to use your good glass with your good camera!