Newton's Universal Law of Gravitation is a physical law that states that there is an attraction force between all objects with mass. The amount of attraction produced between two objects with mass is based on the mass of both objects, the radius of the objects, and the distance between them.
Objects on the earth's surface experience gravity due to the masses of both objects and their distance from each other.
The moon orbits the earth due to gravitation forces between the mass of the earth and moon. The attraction forces between the earth and moon, and sun and earth hold celestial bodies in their orbits.