Gravity depends on both the mass of the two objects pulling on each other, as well as the distance between them. The formula for gravitational force is comprised of a constant, multiplied by the mass of the first object, multiplied by the mass of the second object, then divided by the distance between them squared.
Gravity describes a force that bodies of mass exert on each other. While small bodies produce a negligible effect, large bodies of mass, such as planets and stars, have a significant observable effect. Solid life on Earth adheres to the surface due to the pull of gravity. Although people have a small mass individually, the large mass of the Earth creates a strong enough pull to hold them down.