*Explains* is oversimplification... There is much more to it. Maybe for common people facts seem very important because they seem so interesting. We use the word "fact" as a figure of speech as well. To mean something that is undeniable etc.
But in science facts area a dime a dozen. They do not hold as much importance to scientists. There is a rock on the street, is a fact, but its useless on its own. The purpose of science is to study the facts and observations and make predictions from these facts. That can be independently verified by third parties and always turn out to be accurate.
By predictions I mean, if you study how birds use lift and aerodynamics to fly, you can make a prediction that if you have an object with a certain amount of aerodynamics and a certain amount of air pressure under its wings it will fly. You then use this prediction to make flying machines.
If this prediction is proven to be wrong, the theory will not stand anymore, but this is extremely rare, as a hypothesis has to hold to these tests before it becomes a theory. You can add on more information to the theory as you gain knowledge, but this is a strength for a theory, not a weakness. For example Darwin's theory of evolution explained how evolution works, but later as our understanding of biology progressed, we learned about DNA and retroviruses that further enhanced the theory. It also corrected some of Darwin's classifications but they theory still makes accurate predictions.
So in a nutshell, theories have the highest status in science, much higher than facts. If something is called a theory, its the highest honour you can give to a concept in science.
"Evolution is just a theory"
I think scientists are also guilty of people misusing this term. Its the humility of scientists that after spending 50 years of their lives dedicated to strengthening the work they are doing on a theory, it gets reviewed by peers, it makes accurate predictions and in the end the white haired scientist would say, it's just a theory.
It is because of their humility that they are not arrogant to say, we are 100% right, there maybe a slight chance that we missed an observation and may have made a slight miscalculation, no matter how insignificant the odds are.
They will often spend 15 years of their lives to prove a hypothesis right, when someone shows them that they are wrong, they go over to that person, shake their hand with humility and thank them for correcting them.
Its sad that people take advantage of this humility and mock 100s of years of scientific achievement and make statements like "Evolution is just a theory", while people who have no understanding of the world say with 100% certainty that God did it and try to discredit every scientific understanding or fact, just because it does not suit their superstitious world view.
