A sprocket[1] or sprocket-wheel[2] is a profiled wheel with teeth, or cogs,[3][4] that mesh with a chain, track or other perforated or indented materials.[5][6] The name ‘sprocket’ applies generally to any wheel upon which radial projections engage a chain passing over it. It really is distinguished from a equipment in that sprockets are never meshed together directly, and differs from a pulley in that sprockets have the teeth and pulleys are clean.
Sprockets are found in bicycles, motorcycles, vehicles, tracked vehicles, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or to impart linear motion to a track, tape etc. Probably the most common form of sprocket may be found in the bicycle, where the pedal shaft bears a large 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 chain sprocket mechanism, a practice mainly copied from bicycles.
Sprockets are of varied designs, no more than efficiency getting claimed for each by its originator. Sprockets typically don’t have a flange. Some sprockets used in mixture with timing belts have flanges to keep carefully the timing belt centered. Sprockets and chains are also utilized 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 rather than pulleys. They 
may be run at high speed and some types of chain are so constructed as to be noiseless even at high speed.