A sprocket[1] or sprocket-wheel[2] is a profiled wheel with tooth, or cogs,[3][4] that mesh with a chain, track or other perforated or indented material.[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 directly, and differs from a pulley in that sprockets have teeth and pulleys are simple.
Sprockets are used in bicycles, motorcycles, vehicles, tracked automobiles, and other machinery either to transmit rotary motion between two shafts where gears are unsuitable or to impart linear movement to a track, tape etc. Maybe the most typical form of sprockets sprocket could be found in the bicycle, in which the pedal shaft carries a sizable 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 various designs, no more than efficiency being claimed for each by its originator. Sprockets typically don’t have a flange. Some sprockets used in combination with timing belts have flanges to keep the timing belt centered. Sprockets and chains are also utilized for power transmission in one shaft to some other where slippage isn’t admissible, sprocket chains being used rather than belts or ropes and sprocket-wheels rather than pulleys. They may be operate at high speed and some forms of chain are so built concerning be noiseless actually at high speed.
