The concept of gravity refers to the force that attracts two bodies toward each other. It is a fundamental interaction in nature that keeps planets in orbit around stars, such as Earth around the Sun. The strength of this force depends on the masses of the objects and the distance between them. Isaac Newton first formulated the law of universal gravitation in the 17th century, stating that every mass attracts every other mass. Later, Albert Einstein expanded on this idea with his theory of general relativity, which describes gravity as the curvature of space-time caused by mass.