The Law of Gravity obeys every one of the three Laws of Motion he had already defined. Many years later, across the English Channel, Liebnitz had also developed calculus independently. In what may have been an attempt to 'scoop' the competition, Newton finally published his development of calculus. In the 20 th century, Albert Einstein's Theory of General Relativity showed that Newton's Law of Gravity was a simple representation of something much more elegant.
Gravity is an attractive force existing between and among all objects that have mass.
Well, it is so far, despite Star Trek. There is no magic button or counter force that can make gravity disappear, no such thing as Anti-Gravity. As Newton's Laws of Motion suggest, though, if other forces are exerted in opposite directions, gravity as a force can be canceled out. It is a force between and among all objects that have mass. It's best to think of gravity as a mutual force, one that exists between masses, rather than a force exerted by one object upon another, even though it's sometimes easier to say it that way.