A sprocket[1] or sprocket-wheel[2] is a profiled wheel with tooth, or cogs,[3][4] that mesh with a chain, monitor 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 equipment in that sprockets are never meshed together directly, and differs from a pulley in that sprockets have tooth and pulleys are soft.
Sprockets are used in bicycles, motorcycles, vehicles, tracked vehicles, and other machinery either to transmit rotary motion 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 could be within the bicycle, where the pedal shaft carries a huge sprocket-wheel, which drives a chain, which, in turn, drives a small sprocket on the axle of the trunk wheel. Early automobiles were also largely driven by sprocket and chain system, a practice largely copied from bicycles.
Sprockets are of varied designs, a maximum of efficiency becoming claimed for every by its originator. Sprockets typically don’t 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 in one shaft to another where slippage isn’t admissible, sprocket chains getting used instead of belts or ropes and sprocket-wheels instead of pulleys. They may be run at high speed plus some forms of chain are so built as to be noiseless also at high speed.