Gravitational pull is the invisible force that causes massive objects to pull other objects towards them. For instance, when a person jumps up in the air, it is the earth’s gravitational pull that causes him to return to the ground. All massive objects have gravity, and the bigger they are, the more gravitational pull they produce.
Gravity is one of the four fundamental forces in nature, along with electromagnetic force and strong and weak nuclear forces. While gravity is the weakest of the four forces, it is the only one that functions over great distances. Additionally, gravity’s effects do not take time to propagate; the pull is instant.
It is the sun’s gravitational pull that keeps the Earth and other planets locked in their orbits. Because the sun is the largest object in the solar system, it has the most gravity. The solar system itself orbits a supermassive black hole at the center of the Milky Way galaxy. Such massive black holes have enough gravity to bend rays of light.
Moons and other satellites orbit around the planets, rather than directly around the sun, because their proximity to the planet means that the most gravitational pull is coming from the planet instead of the sun.