how a pulley works and mention its mechanical advantage?

a pully work using the frictional and gravitational force when using a pully you will see that your doing work and transfering ernergy from one state to an other that is the mechanical advantage.

The mechanical advantage of a pulley is a number that represents the ratio of the force being applied to an object (like a weight being lifted) divided by the force that has to be applied at the other end to get the object to move.