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 material.[5][6] The name ‘sprocket’ applies generally to any wheel where radial projections engage a chain moving over it. It is distinguished from a equipment in that sprockets should never be meshed together straight, and differs from a pulley for the reason that sprockets have teeth and pulleys are smooth.
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. Perhaps the most typical form of sprocket could be found in the bicycle, in which the pedal shaft bears a huge sprocket-wheel, which drives a chain, which, in turn, drives a little sprocket on the axle of the trunk wheel. Early automobiles were also largely driven by sprocket and chain mechanism, a practice largely copied from bicycles.
Sprockets are of varied designs, a maximum of efficiency being claimed for each by its originator. Sprockets typically do not have a flange. Some sprockets used in combination 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 another where slippage isn’t admissible, sprocket chains becoming used rather than belts or ropes and sprocket-wheels rather than pulleys. They may be operate at high speed plus some types of chain are so built as to be noiseless actually at high speed.