Newton's law of gravitation is called gravitational law because this law holds true for all bodies, whether massive or microscopic placed everywhere in the universe.
Thus, as it is applicable universally, it is called universal law.
This theory describes and explains the questions of day to day life like, why apple falls down to the ground from tree, how are we able to stand and walk on earth, what locks the earth in orbit and keeps it revolving around the sun. This law explains not only the attraction between bodies in universe but also the strength of attraction between the objects.