A gearbox, in essence, acts as being the middleman, catching the baton from your prime mover (may or not it's an electric motor or an inner combustion motor) and passing it on to your driven shaft – a propeller shaft of a motor vehicle or an industrial device’s spindle. https://gearbox08641.blogocial.com/the-smart-trick-of-gearbox-that-nobody-is-discussing-69564754