1. Mass: The more massive an object is, the stronger its gravitational pull. This is why you feel a stronger gravitational pull from the Earth than you would from a small rock.
2. Distance: The farther away you are from an object, the weaker its gravitational pull. This is why you don't feel the Earth's gravity as strongly when you're in a plane, for example.
In short, the strength of gravity is directly proportional to mass and inversely proportional to the square of the distance.
This relationship is described by Newton's Law of Universal Gravitation:
```
F = G * (m1 * m2) / r^2
```
Where:
* F is the force of gravity
* G is the gravitational constant (a fixed value)
* m1 and m2 are the masses of the two objects
* r is the distance between the centers of the two objects
