Hydraulic lift is a device for moving objects using the force created by the pressure on a fluid inside a cylinder that moves the piston up. Incompressible oil is pumped into the cylinder, which pushes the piston up. When the valve opens to release the oil, the piston is lowered by the force of gravity.
The principle of hydraulic lifts is based on Pascal's law of force or motion, which states that a change in pressure on an incompressible fluid in a confined space is passed evenly throughout the fluid in all directions.
The concept of Pascal's law and its application to hydraulics can be seen in the example below, where a small amount of force is applied to an incompressible fluid on the left to create a large amount of force on the right.