A sprocket[1] or sprocket-wheel[2] is a profiled wheel with the teeth, 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 gear in that sprockets are never meshed together directly, and differs from a pulley for the reason that sprockets have tooth and pulleys are clean.
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 even to chain sprocket impart linear movement to a track, tape etc. Perhaps the most common form of sprocket may be within the bicycle, where the pedal shaft carries a large 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 powered by sprocket and chain system, a practice largely copied from bicycles.
Sprockets are of various designs, no more than efficiency becoming claimed for every by the 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 utilized for power transmission from one shaft to another where slippage is not admissible, sprocket chains getting used rather than belts or ropes and sprocket-wheels rather than pulleys. They could be run at high speed and some forms of chain are so built concerning be noiseless actually at high speed.