The cameras that can use the EF-S mount are the Canon EOS 300D, 350D, 400D, 450D, 20D, 20Da, 30D, and 40D digital SLRs. These cameras can all use both EF and EF-S lenses.
The "S" in EF-S stands for "short back focus", which means that the rear element of the lens is closer to the image sensor than on regular 35 mm SLR cameras. The proximity of the rear element to the image sensor greatly enhances the possibilities for wide angle and very wide angle lens, enabling them to be made smaller, lighter (containing less glass), faster (larger aperture) and less expensive. Most current Canon EF-S lenses are wide angle