There are two kinds of force that dominate our everyday reality: gravitational force and electromagnetic force. Gravitational force is the force that attracts objects to one another. It is what keeps the planets in orbit around the sun, and what keeps us on the surface of the Earth. Electromagnetic force is the force that governs the behavior of electrically charged particles. It is responsible for light, radio waves, and other forms of electromagnetic radiation. These two forces are the most fundamental forces in the universe, and they are responsible for much of the behavior we see in the world around us.