One observes an apple fall from to the earth. An apple falls to the earth every time it is dropped and wherever it is tried. Whatever you call that thing that explains why that observation occurs is a law. It would be absurd to call that thing a theory, because you observe
One can see the remains of living things in the fossil record, but one cannot see them come into being. One has an idea of how they come into being, but one cannot create or replicate the conditons in order for one to observe the phenomenon take place. Hence, one does not really know how life comes into being. One can only theorize.
And fossils all appear to change over time, there have never been exceptions to this rule. I.E. "Modern" fossils are NEVER found in locations where less modern fossils are. This is a bit harder to "prove" to the dubius than the apple falling, only one falling apple being enough to demonstrate the point. But after litterally millions of fossils have been collected from all over the world, the evidence of life changing, "Evolving", over time always holds.
There are two meanings of word "Evolution". The FACT that evolution happened is proven well enough to be considered beyond doubt among those who have seriously studied the subject. Then there is Evolution THEORY, which is the method that Evolution operates. This is what Darwin proposed by his "survival of the fittest" method. The details of this are still being worked out, but absolutely none of those details contradict the evidence that Evolution indeed happened.
My daughter studies Music THEORY in college. There is no doubt that Music exists. But the study of how music works is called Music Theory.
The FACT of Gravity you don't doubt. But the THEORY of how Gravity operates is actually quite more in doubt than the THEORY of how Evolution operates.