A "theory" is an explanation of observable phenomena, when the actual facts cannot be empirically proven. A good theory is one that is consistent with everything that we can observe or measure.
For example, scientists held many theories about the appearance, shape, and characteristics of the atom before the electron microscope made those things nearly observable.
Evolution is a longstanding theory about the origin of earth's species. It remains a useful teaching tool to explain the divisions of life on earth (genus, species, etc.). Unfortunately, it has become an article of faith among the world's Leftists - none of whom are actual scientists - so that anyone denying it is immediately branded a heretic (or similar).
But the more people look into it the more overwhelming its flaws and shortcomings have become, so that among actual scientists it is nothing more than a convenient teaching tool, with the final conclusion on the origin of species yet to be determined.
Creationism is not science but it is essentially true: God created everything out of nothing...we just don't know how.
