I would define science as the quest to find the intrinsic truths of the cosmos, outside of human experience. That is to say, it is the quest to find the things in the universe that are true for everybody.
Obviously nothing is 100% sure, but when there is no genuine alternative theory, or when one theory is much more supported by evidence than another, we are forced to accept it. When a theory is accepted by the vast majority of scientists, it becomes a scientific fact. There are definitely facts in science. For example a study found that 95% of the top scientists in the US are atheists. That's not a theory, it's a fact. We could come up with many theories as to why that is the case, but we can't label that anything other than a fact.
We can see, very clearly, that evolution has occurred. We would have to have the very obvious theory that life will continue to evolve from this point, but the amount of evidence that shows that life has evolved to now is undeniable (unless you don't look at the evidence). Evolution is a fact - it has actually happened and there are no other explanations with evidence to back them up for what we've observed.