Mechanical Advantage - achieved through simple machines

Mechanical Advantage is a measure of the amount of force 'gained' after using a machine to move an object. 

The video below by the Efficient Engineer, explains mechanical advantage with many simple machines

Note on things not explained in the video:

Wheels for all intents and purposes are levers and provide their own mechanical advantage

When it comes to gears and pulleys a 'gear ratio' is not exactly the same as mechanical advantage