Evolution is quite simply descent with modification.
As steveandersen mentioned above, you cannot separate small-scale and large-scale evolution. Also, evolution doesn’t have to be presented in a manner that is overly complicated (though the study of evolution can become extremely complex).
Basically it works like this: all living things on earth have a history, that has changed over time, and different species share a common ancestor.
From that point we can get into more specific branches of evolution such as speciation, mutation, genetic drit, migration, genetic variation, coevolution, natural selection, differential reproduction, gene frequency, gene flow, somatic mutations, morphology, adaptation, sexual selection…and about three dozen more separate conversations!
I think there are a few issues that trip people up about evolution.
It is not necessarily progressive. That is a stipulation some people read into evolution (and a connotation of that word), but scientific evolution has nothing to do with qualifying terms like “better,” “improved,” “good.” Those are human judgements.
Evolution is a scientific theory. People that say “it is only a theory” need to remember that there is a huge difference between a scientific theory and Jim Bob’s theory on UFO abduction or zombification.
A Scientific theory does not mean an unsubstantiated guess or hunch. A scientific theory is a logical, self-consistent model of observed data that is predictive and testable. The theory of evolution is often refined, tested, and debated by modern scientists, especially as more technologically advanced equipment has made more data available. Yet, the model remains and is well established as basic biological fact.
I’m glad the Church has no problem with Theistic Evolution. Why deny the obvious?