An escalator is a continuous belt that is moving on chains and completing the circuit. The belt wraps around two sets of gears, one at the top and one at the bottom, forming a complete circuit. The belt is driven by an electric motor that makes the belt move along the gears.
The belts move through the gears at the bottom, loop around and then connect at the top forming a continuous circuit that keeps moving. The setting of the belt allows the belt to form steps as it moves in to the open while the belt flattens and disappears as it moves around the gears.
At the core of an escalator, there are pairs of different chains that are looped around a pair of two gears. These gears are driven by the use of an electric motor at the top end. This in turn rotates the loops of chain allowing the whole system to run.
There is another pair of gears at the lower end of the escalator and hence, the chains rotate in a continuous loop around two opposite pair of gears through the use of an electric motor. Considering this, the working of an escalator is quite simple and easy to understand by nature.
