The way I was raised makes it hard for me to see something as being fact, and unproven theory at the same time. It is contradictary to me.
It is miss-leading to me.
Let's try again then.
It is a fact that things fall down if let go with no support. Right?
So how does this happen? Newton explained it through the attraction that masses have. This is the "how" and is a theory of gravity. His theory gave equations for calculating how fast things would fall.
Now we have what we might carelessly call "gravity" meaning two things. One is the fact that things fall and the other is a theory on how.
It turns out that if you are very nit picky or dealing with some situations that Newton's theory was "wrong" (or not perfect or whatever word you want to use). Did things stop falling down? No!
Now we have Einstein's theory of gravity. It predicts different results under some circumstances. The difference in predictions was used to see who was right. However, there is a good chance that Einstein's theory is also wrong. There are some problems to be sorted out. When they are we might have a third theory of gravity.
How about a simpler analogy:
Bob has arrived at your doorstep to visit. That is a fact. You don't see his car in the drive way but it could be up the street. The buses don't run very close. He could have hitched a ride. Bob is lazy. Bob doesn't like to spend money. If he doesn't tell you how he got there you might form your own "theory" (more like an hypothosis). He drove but parked up the street to avoid the mud near your house which would dirty his car.
It is a fact that he got there, he was transported, and you have a theory of transportation.
We use the word "evolution" to mean both the fact that evolution has happened
and the Theory of Evolution (ToE). Sometimes it isn't clear when just the one word is used.
And it is simply fact that it has happened. Once upon a time (it doesn't matter exactly the amount of time ago) there were no mammals, no birds, no reptiles. At a later time there were reptiles but no birds and mammals. Now they are all here. Either there were a whole bunch of individual creation weeks or the later life was born of the earlier. This is what scientists of a couple of hundred years ago went through. They were predominantly believers in the story in Genesis. When they found more and more evidence for the changes in life they had to keep adding more and more and more creation weeks until it began to get silly.
But if not those creation weeks then how did the life change? That was the question that Darwin answered. Of course with what we've learned since the orginal "many weeks" theory would have to have 10,000 of creation weeks and would clearly be absurd as a theory.
Also you are having trouble with the word "proven" (or "unproven"). In mathematics the word proof is used very carefully. It means absolutely and completely for sure true. The word proof is used somewhat similarly in science. Since we can't have mathematical proofs for anything we avoid the word proof.
That doesn't mean that there is much doubt about some "unproven" theories. There is probably more doubt about general relavity (Einstein's theory of gravity) than there is about the ToE. A theory isn't proven it just gets to be more and more trusted. Some of our scientific theories are very trusted indeed. The ToE is one of them.
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