A sprocket or sprocket-wheel is a profiled wheel with teeth, cogs or even sprocket that mesh with a chain, track or other perforated or indented material.The name 'sprocket' applies generally to any wheel upon which are radial projections that engage a chain passing over it. It is distinguished from a gear in that sprockets are never meshed together directly, and differs from a pulley in that sprockets have teeth and pulleys are smooth.