Gravity

Gravity is a property of matter. The bigger an object is, the more gravity it will have. When an object has gravity, it will pull other objects toward it.

Examples of gravity:
 * The Sun has lots of gravity, so it can hold all the 8 planets in the solar system and instead of the planets flying off, they orbit around the Sun.
 * The Earth has gravity, so it can keep the Moon orbiting around it.