Gravity is a force that attracts every Object that has mass towards every other object that has mass towards every other object. Mass is the amount of matter an object, or body contains. The amount of Gravitational Pull between two bodies depends on the mass of the two bodies and the distance between them. The greater the masses the greater the force. The further the distance between them, the smaller the force. The amount of gravitational pull between bodies is very massive, such as a planet.
This is called the Law of Universal Gravitation. It was first written by the English scientist Sir Isaac Newton (1642-1727). This law of gravity explains how the gravitational pull between bodies causes the planets to orbit the sun. A body has a gravitational field around it. Any other object in the field experiences a pull from the body, which pulls the object towards it.