Canon SLRs use interchangeable lenses. You need to get the correct mount (Canon) and select the correct type. Point and shoot have adapters, but not interchangeable lenses.
The short answer is yes. You can go to e-bay and purchase any lens you want. I have yet to purchase any brand name lens that I can't interchange with my Nikon and Canon.
This depends on what type of camera it is. For the most part the only kind of digital cameras that use interchangeable lenses are the SLR models. If it doesn't have a detcahable lense, then no.
Some Canon models allow interchangeable lenses while others do not. You will have to do research on your own to find out, since you did not specify what model you had. Start with your owner's manual.
