When something is controversial, people think different things about the same subject and talk about it a lot. So here goes. Evolution is a thing some people don't believe in. That makes it controversial.
Evolution is the idea that says living things change over time as their environments change.
That idea, of things changing over time, disturbs some people and they do not believe it. Just yourself - and the time to notice a few things. After the shower is off, or you're out of the tub, step into the center of the room. Do not grab a towel. Relax with your arms at your sides.