I believe that in science, the working definition is "descent with modification." In other words, as organisms reproduce, the new organisms are not exactly the same as the 'parent' organisms. Each successive generation is changed in very small ways, and the accumulation of those changes leads to gradual change in the population of those organisms. Enough time and enough changes, and you have a different species of organism. Or a different genus. And so on.
The definition covers what some refer to as 'micro-evolution,' which describes minor changes within a species or sufficient changes to produce a new species which is still close enough to the original, though by definition they cannot interbreed. It also covers macro-evolution, though a significant amount of work needs to be done to demonstrate it, which is where the gulf between science and religion exists on the issue.
I think Aron Ra's YouTube channel does a good job of explaining evolutionary concepts and responding to many of the attempts to discredit the theory. For me, the question is moot from an existential point of view, but I do like science and find the work done so far to be fascinating, if a bit science-fictiony to someone lacking in the higher levels of biological education. The scientific method isn't perfect, but over the long haul I think it does the best job of finding answers. If evolution doesn't work as explained, we'll learn in time.