gravity is a very weak force when compared to other atomic forces. it is thought that gravity is a force that "leaks" out of different dimensions to our current set. gravity is proportional to the mass of the objects and the distance between them, every object has gravity. if gravity was a strong force your keyboard would be attracted to your face with much greater force than it is now.
A good way to picture gravity is to take a sheet of plastic wrap stretched tightly over a large bowl, then place an object in the middle. the shape of the plastic will simulate the force of gravity as you move away from the object. take a pea that is round and roll it along the plastic, it curves around the other object and, with a bit of force will "orbit" the larger object, while still making a small dent from its own gravity. now extrapolate this to the 4 dimensions and you will have a better understanding of how gravity is thought to work.
as to this topic: he is right, why all the flaming? I guess i over estimated the intelligence of AT, though, that seems to happen a lot.