Gravity is the force that attracts objects with mass. The earth for example attracts the moon towards it because the earth and the moon both have mass. Furthermore, the sun attracts the earth, and all the other planets, making them revolve around the sun.

Another way to think of this attraction is as follows: suppose you have a big rubber sheet, spread out flat. If you place a massive object, like a ball, in the center of the sheet, the ball will cause the sheet to deform, bending the sheet downwards towards the object. Now imagine you put another ball on this sheet. If the ball is light enough, it will follow the deformed path, and fall towards the larger ball, as if it were attracted to it. This simulates the effect of gravity on these balls. If you think of this sheet as the space around a massive object, gravity will deform this space to attract massive objects toward it.

Gravity acts on an object with mass, attracting it to other massive objects. This theory leads to the reason why an apple falls to the surface of the earth, and why the earth revolves around the sun.

I hope this answers your question!

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Gravity is a force that extends throughout the universe. For gravity that we are familiar with, two objects will exert gravitational force equal to the product of their masses divided by the square of the distance between them, much as light illuminates less the farther away you are.

The presence of mass bends space-time and the gravitational attraction is objects being drawn toward each-other as space contracts, but the math behind that calculation is vast and interesting.

There is also a gravity-like force that is driving the universe apart. We know that this force exists because we see its effects, but I don't believe anybody has a good idea of how or why.