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 passing over it. It is distinguished from a gear in that sprockets should never be 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 automobiles, and other machinery either to transmit rotary movement between two shafts where gears are unsuitable or to impart linear motion to a monitor, tape etc. Maybe the most typical form of sprocket may be within the bicycle, in which the pedal shaft bears a big 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 mainly copied from bicycles.
Sprockets are of various designs, a maximum of efficiency being claimed for each by its originator. Sprockets typically don’t have a flange. Some sprockets used with timing belts possess flanges to keep the timing belt centered. Sprockets and chains are also used for power transmission from one shaft to another where slippage isn’t admissible, sprocket chains being used rather than belts or ropes and sprocket-wheels rather than pulleys. They could be run at high speed plus some types of chain are so constructed concerning be noiseless also at high speed.