This happened a few nights ago. Her question informed me that I was going a little too fast. Time to slow down and fill in the blanks. Impressive for someone as long-winded as me. Needless to say, I elaborated.
Gravity is created by mass.
The more mass something has, the more gravity it generates. Imagine equally sized containers of lead and, say, wood. It only pulls. It is the pull of Earth's gravity that keeps you on the ground, keeps your coffee in its mug, holds down the atmosphere and oceans, and keeps the Moon in its orbit. Without the Earth's gravity, our Moon would fly off into space, its own momentum carrying it in a straight line.