Think of this:
An object is moving in a straight line. Gravity pulls in another direction than the object is going. Therefore, The object will often times revolve around the point of high gravity.
Object moves this way -->
Gravity pulls north
the object will go in a orbit with an angle halfway between the object's original route, and the point of gravity. It is very difficult to explain on the computer, but I hope this shows a basic answer to your question. (for Earth it is this way at least)