Gravity is like when you sit on a bed and loose stuff on it is attracted to your bottom; they move over to you. Well, it's like that with the Earth, but the impression the bottom (Earth) makes with the bed (space) is an all-around 3D one; loose bodies (the moon, asteroids, etc) are attracted to it. A heavier bottom (the Sun) will attract more loose things (planets, asteroids, moons, etc). This is a gravity well.

https://www.qrg.northwestern.edu/projects/vss/docs/space-environment/3-whats-a-gravity-well.html

Gravity is like when you sit on a bed and loose stuff on it is attracted to your bottom; they move over to you. Well, it's like that with the Earth, but the impression the bottom (Earth) makes with the bed (space) is a 3D one; loose bodies (the moon, asteroids, etc) are attracted to it. A heavier bottom (the Sun) will attract more loose things (planets, asteroids, moons, etc). This is a gravity well.

https://www.qrg.northwestern.edu/projects/vss/docs/space-environment/3-whats-a-gravity-well.html