Cement and Concrete
This may come as a surprise to you: Your sidewalk, driveway, patio, and paths are not made of cement. Rather, they are made of concrete which contains cement -- Portland Cement to be exact.
Basic concrete is a mixture of rock, sand, and cement. In combination with the oxygen in water, the three dry elements bond together to make good old fashioned concrete. You know -- the stuff in your yard that usually has cracks in it that you're always trying to patch.