Can i have 3 examples of gravity? what is gravity? how does gravity work? does gravity only work on objects that have only mass?

Gravity, or gravitation, is a natural phenomenon causing all things with mass to be brought toward one another. This includes objects ranging from atoms, photons, to planets and stars. Some examples of gravity include: Holding the gases in the sun, causing a ball you throw up to come down again. And causing a car to coast downhill even when you aren't stepping on the gas. Gravity can, indeed, work on objects that DO NOT have mass. 

Hope this helped at least some.

Gravity- The force that attracts a body towards the center of the earth.
It works when you drop something it goes straight down to the earth and everything weighs something.