A single force on an object usually just makes it move. To change the shape of an object you need more than one force acting on it. If you pull one end of a spring and the other end is free, the whole spring just accelerates. To stretch the spring, you must pull on both ends, in opposite directions. One force holds the object while the other pulls it out of shape.
Compressing works the same way. To squash a spring you push on both ends, towards each other. Pushing on only one end would just shove the spring along the table, so there must be two forces.
Bending also needs more than one force. If you hold a plastic ruler at both ends and push down in the middle, the forces at the ends and the force in the middle act in different directions and the ruler bends. A stretched spring, a squashed spring, a rubber band and a bent ruler are all elastic objects being distorted by two or more forces.
When an object is not moving, the forces on it are balanced. A spring is held stretched because the forces pull outwards at each end and are equal in size.
