How Does Gravity Affect Planets?

Sir Isac Newton was super at ALL forms of math, and I did a cheat sheet Test in college on him. Info on him in this area is very easy to find and in depth!
One of the best I've seen is at pbs.org, and it's two one hour shows and explained on level Neophytes can understand! No one held my hand in college!
Logic101

The force of gravity was influential in the formation of the elements after the Big Bang. This force of attraction also caused the formation of stars and planets. This is the force which holds the planets in motion around the Sun and the Sun in motion around the galaxy.

It keeps them orbiting the sun and the moons orbiting the planets

Its because of gravity they are round.