it says, "forces on a object that do not change the motion of the object" this is explaining what a balanced force is. it also says, "the rope will not move because there is the same force on both sides." because there is the same amount of people the force will be equal.
next is unbalanced force, a example is a bigger man with more force bringing the smaller man with less force up, the force is not balanced because there is not the same force, unlike balanced force.
another example of a unbalanced force is, a side with more "n" than a side with less "n" the force is unbalanced because 