These laws of motion were found to work for objects in the heavens, as well as objects on Earth, thereby making Newton the first astrophysicist. When one body exerts a force on a second, the second body exerts an equal and opposite force upon the first. B. Newton distinguished between an object's mass, which is how much matter it contains, and its weight. A person who is on the moon is attracted by the moon's gravity less than that same person will be attracted to the Earth by Earth's gravity. That person's mass is the same in both places, but the weight is different.
Weight is a force, mass is the amount of matter.
C. Newton determined that for the planets to orbit the sun in elliptical trajectories, they must be subject to a force that decreases proportional to the square of their distance from the sun. In addition, the force must be proportional to the masses of the sun and the planet. This is the Law of Universal Gravitation because we can extend this equation to any two objects, in the universe. For example 'M' could be the mass of Jupiter, while 'm could be the mass of its satellite Europa. Therefore all massive objects are gravitationally attracted to all other massive objects in the universe.