A mechanical watch is a watch that uses a clockwork mechanism to measure the passage of time, the mechanical watch is driven by a mainspring which must be wound either periodically by hand or via an automatic winding mechanism.
Its force is transmitted through a series of gears to power the balance wheel, a weighted wheel which oscillates back and forth at a constant rate. Watch the video from Emanuel Ion for more info:
A device called an escapement releases the watch’s wheels to move forward a small amount with each swing of the balance wheel, moving the watch’s hands forward at a constant rate.
The escapement is what makes the ‘ticking’ sound which is heard in an operating mechanical watch. The internal mechanism of a watch, excluding the face and hands, is called the movement. All mechanical watches have these five parts:mainspring, gear train, balance wheel, escapement.