A fact is something that happens. If you read “theory” as “model” it makes more sense.

So evolution occurs. Our model of it is crap. Gravity exists. But Newtons model of gravity only works for human things approximately human size and speed. When it gets too big and fast we need Einstein’s model (general relativity) to explain things, if it gets too small we need quantum gravity.

Or put differently: it is a fact that I wrote these words. If you tried to describe my words with a theory/model, and it predicted which words I would write next, then you have a decent theory/model.

I hope this helps