Gravity is one of the fundamental forces of nature that exists in the universe. It is responsible for the attraction between objects with mass or energy. According to our current understanding of gravity, it is described by Einstein's theory of general relativity.
According to general relativity, gravity arises due to the curvature of spacetime caused by the presence of mass and energy. Mass and energy tell spacetime how to curve, and the curvature of spacetime, in turn, tells mass and energy how to move. Objects with mass or energy move along the curved paths created by the presence of other massive objects.
In this framework, the force of gravity is not a force in the traditional sense, but rather the effect of objects following the curved paths in spacetime. The more massive an object is, the greater its curvature of spacetime, and the stronger its gravitational influence.
Gravity acts over long distances and affects all objects with mass or energy, no matter how small or large. It is responsible for keeping planets in orbit around the sun, moons around planets, and galaxies bound together. It is a relatively weak force compared to the other fundamental forces, such as electromagnetism, but its effects become significant on large scales due to the cumulative effect of mass.
While general relativity provides a highly successful description of gravity on large scales, there is ongoing research to understand how gravity can be reconciled with the other fundamental forces, such as quantum mechanics, at the smallest scales. The search for a theory of quantum gravity is an active area of study in theoretical physics.