A sprocket[1] or sprocket-wheel[2] is a profiled wheel with tooth, or cogs,[3][4] that mesh with a chain, track or other perforated or indented material.[5][6] The name ‘sprocket’ applies generally to any wheel upon which radial projections engage a chain passing over it. It is distinguished from a equipment in that sprockets are never meshed together directly, and differs from a pulley in that sprockets have tooth and pulleys are clean.
Sprockets are used in bicycles, motorcycles, vehicles, tracked vehicles, and other machinery either to transmit rotary movement between two shafts where gears are unsuitable or even to impart linear motion to a track, tape etc. Probably the most common form of sprocket may be within the bicycle, where the pedal shaft carries a big sprocket-wheel, which drives a chain, which, in turn, drives a little sprocket on the axle of the trunk wheel. Early automobiles had been also largely powered by sprocket and chain mechanism, a practice largely chain sprocket copied from bicycles.
Sprockets are of various designs, a maximum of efficiency being claimed for every by its originator. Sprockets typically do not have a 
flange. Some sprockets used with timing belts possess flanges to keep carefully the timing belt centered. Sprockets and chains are also used for power transmission from one shaft to some other where slippage isn’t admissible, sprocket chains getting used rather than belts or ropes and sprocket-wheels instead of pulleys. They could be operate at high speed plus some kinds of chain are so constructed as to be noiseless also at high speed.