Question: Why does gravity occur?

Claudia Bonfio answered on 6 Jun 2018:

Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the Sun and what keeps the moon in orbit around Earth. The gravitational pull of the moon pulls the seas towards it, causing the ocean tides. Gravity creates stars and planets by pulling together the material from which they are made.
Why does it occur? Unfortunately the answer is a bit complicated… The general theory of relativity describes gravity as a consequence of the curvature of spacetime (I like to think of it as a sandy surface, rather than a flat surface) caused by the uneven distribution of mass (like the Sun). So the presence of the Sun induces a sort of hole that “attracts” the planet towards it. Then the centrifugal force allows the planets to not collapse on the Sun.