Pulleys are a simple form of machine. They make jobs easier to do. Pulleys are usually used to lift things.
If we ignore friction the more pulleys in a pulley system the less effort you have to use to lift up a certain load.
If we look at the pulley system and imagine the effort on the right hand rope pulled down 1m. This means that 1 m of rope must come over the pulley and so the load rises 1 m.
This means that the velocity ratio of our pulley system is 1.
However if the pulley is 100 % efficient and the velocity ratio is 1 then the mechanical advantage is also 1 and that means that the load and effort are the same.
(This particular pulley arrangement does not really make the job easier except that using your own weight as part of the effort means that there is less effort in your arm muscles.)