A sprocket[1] or sprocket-wheel[2] is a profiled wheel with the 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 moving over it. It 
is distinguished from a gear in that sprockets are never meshed together straight, and differs from a pulley in that sprockets have teeth and pulleys are easy.
Sprockets are used in bicycles, motorcycles, vehicles, tracked automobiles, and other machinery either to transmit rotary movement between two shafts where gears are unsuitable or even to impart linear movement to a track, tape etc. Maybe the most typical form of sprocket may be within the bicycle, where the pedal shaft bears a sizable sprocket-wheel, which drives a chain, which, subsequently, drives a little sprocket on the axle of the rear wheel. Early automobiles had been also largely driven by sprocket and chain mechanism, a practice generally copied from bicycles.
Sprockets are of varied designs, a maximum of efficiency getting claimed for every by its originator. Sprockets typically do not have a flange. Some sprockets used in mixture with timing belts possess flanges to keep the timing belt centered. Sprockets and chains are also used for power transmission in one shaft to another where slippage is not admissible, sprocket chains getting used instead of belts or ropes and sprocket-wheels rather than pulleys. They could be operate at high speed and some kinds of chain are so built concerning be noiseless even at high speed.