Gravity is defined as the attraction between objects. All objects with mass are affected by gravity. (Mass is what the matter is made of.) Gravity acts like a magnet pulling objects together. The Earth has gravity. Gravity holds everything close to this planet. Trees, water, animals, buildings, and the air we breathe are all held here by gravity. We need gravity for us to stick on the ground and not to float into the air. It stops objects from falling off our planet earth.