A force is a push or a pull. Force gives an object the energy to move, stop moving, or change direction. It has both magnitude and a direction. Newton's first law states that an object's velocity cannot change unless it is acted upon by a force. The four fundamental forces in the universe are: gravitational force, electromagnetic force and strong and weak forces at the atomic level. All other forces that we see in day to day life are based on the interactions of these four fundamental forces. These non-fundamental forces can be in form of centripetal force, friction, elastic force, tension etc.