This law is confusing me. If everything needs an equal and opposite reaction how do things move? Surely everything should be stationary if this law is true?
The forces act on different objects. For example, consider a ball dropped from a building. Ignoring drag, there is only 1 force acting upon it, which is the pull of gravity from the Earth acting on the ball. The other force that makes this an equal and opposite reaction is the ball pulling on the Earth. The forces are acting on different objects, therefore both objects move.