Gravity is a force between two objects with mass. It pulls things together. You have mass, and the Earth has mass, so gravity tries to pull you and the Earth together.

The gravitational force is much bigger for more massive objects. The Earth has a lot of mass, which is why it can hold you down. You can't feel the gravity attracting you to smaller objects, like your house or other people. That's because these things aren't anywhere near as massive as the entire Earth.

OK, so you know what gravity is. But how does it actually pull stuff together? Actually, scientists aren't sure. There is a theory that gravity is made up of little particles called gravitons, just like light is made up of little particles called photons. But we've never seen a graviton! So we're not actually sure they exist.