Gravity is rather a colloquial term used to refer to earth's gravitational field, which is a result of the gravitational force. The gravitational force, by definition, is a force that acts universally on all bodies, in an attractive way.
Another of the 4 basic forces of nature, electromagnetic force is dual natured, ie, it could be both attractive or repulsive, depending on polarity or sign of charge.
But gravitational force is universally attractive.
Gravity is directly propotional to the mass of earth
if u go deep under the earth the mass under u reduces 
 so gravity reduces