More pulleys allow you to distribute the force necessary to lift an object. Like if you had to lift a 40 N object, instead of having one pulley, you can have four pulleys with tensions of 10 N each in the ropes.
No, the force decreases on each pulley as the number of pulleys increase. Like in my 40 N example, the 4 pulleys each have a tension of 10 N in their ropes. However, if you only had two pulleys, they each would have 20 N tensions in their ropes. Take all the pulleys that are contributing to lifting into account.