What dose the theory of evolution tell us about living things

it tells us that it is the change in the characteristics of a species over several generations and relies on the process of natural selection

Explanation:

Natural Selection: The process where organisms have better adapted to their environment and tend to survive and produce more offspring than those without the adaptations

With that dictionary definition we know that we develop certain characteristics in order for survival. The characteristics are developed over multiple generations. One example is that we have a part of our body that we needed before, but no longer need as we don't need to be immune to poisonous foods (or that's what our body tells us)