“Is gravity a theory or a law?”
We’d both agree gravity is a fact.
The law of gravity probably says things with mass attract.
The theory of gravity attempts to explain why. Gravitons are part of the theory of gravity. No one has ever seen a graviton, which is postulated to carry the force of gravity.
But the theory predicts gravitons. When we find them, the theory is strengthened.... but what if we don’t? The law still applies, though.
Okay, gravity is a fact and, conversely, evolution is a theory.