In the world of mechanical power transmission, gear drives have a very special and prominent place. This is actually the the majority of preferred technology if you want to transmit considerable power over a brief distance with a constant velocity ratio. The system of gear drives is very simple – one’s teeth, which are cut on the blanks of the apparatus wheel, mesh with one another to transmit power. To avoid slipping, the projections on one disc mesh with the recesses on other disc in gear drives.
This technology uses different 
types of gears for power transmission. In fact, it could transmit power not only between parallel shafts, but also between nonparallel, co-planar, and gear chain china intersecting etc. shafts.