Gravity (phenomenon) is neither a theory nor law, in a similar way that a cat is different from a picture of a cat or a dictionary entry describing the word cat or our collective understand of what a cat is. At the same time, gravity is also BOTH a theory and a set of laws in the same sense that you could point to a picture of a cat and say "that's a cat right there", and no one would correct you. The distinction seems silly, but it is important. Theory, law, etc are structures/lenses through which we understand and predict things. A sort of formalized collective metacognition is the basis of science, and this is why we have these terms and distinctions. And theories and laws are fundementally different things in a way that's may be best expanded by critically reading the resources provided by the other commenter.