double pulley system
System consisting of two pulleys with a rope running around them to lift a load. Using two or more pulleys reduces the amount of effort needed.
load 
Weight whose inertia exerts a force opposite to the force exerted on the rope.
pulley 
Device with a grooved wheel (sheave wheel) around which a rope passes to transmit the effort exerted on the load.
rope 
Cord that slides on the pulley and is pulled to lift the load.
effort 
Force exerted on the pulley’s rope to lift the load.