Gravity is one of the significant forces of the universe. It is the force that draws other objects closer to the center of another object. The bigger the object, the higher its force of gravity and nearby objects are accelerated towards the big mass.
It is this force of gravity that keeps the planets in the solar system orbiting around the sun. The suns gravitational pull is stronger than those of the planets hence pulls the planets on their orbits around the star. Gravity also played a part in the formation of the planets. Gravity caused the condensation of dust and rocks into a mass that continually attracted more matter as it gained mass (due to gaining more associated gravitational pull).