An orbit is a regular, repeating path that one object takes around another object or center of gravity. Orbiting objects, which are called satellites, include planets, moons, asteroids, and manmade devices. Objects orbit each other because of gravity. Gravity is the force that exists between any two objects with mass. Every object, from the smallest subatomic particle to the largest star, has mass. The more massive the object, the larger its gravitational pull. Gravitational pull is the amount of force one object exerts on another object.

Source: National Geographic