Here's why:

* Gravity is a force of attraction between any two objects with mass. The Earth has a large mass, so it exerts a strong gravitational pull on objects near its surface.

* This pull is what we experience as weight. The heavier an object is, the stronger the gravitational pull, and the harder it is to lift it off the ground.

* The force of gravity acts downward towards the center of the Earth. This is why objects fall to the ground when dropped.

While gravity is the primary force responsible for holding objects to a surface, there are other forces at play as well, depending on the specific situation:

* Friction: This force opposes motion between two surfaces in contact. Friction helps keep objects from sliding off a surface.

* Normal force: This is an upward force exerted by a surface on an object in contact with it. It balances the force of gravity, preventing the object from sinking into the surface.

Let me know if you have any other questions!