Catoptromancy is a big word that means telling the future by looking into a mirror. It was something people used to do a long time ago to get answers or guidance from the spirits. They believed that if they looked into a mirror and saw something strange or unusual, it was a sign of what was going to happen in the future.
Nowadays, we don't really use catoptromancy anymore because we have other ways to get answers like talking to people or looking things up on the internet. But some people still like to use mirrors to help them meditate and focus on their thoughts.
If you ever want to try it out, you can sit in front of a mirror and stare at your reflection for a while. Maybe you'll see something interesting, but remember, just like with any kind of prediction or fortune-telling, it's not always accurate. So, don't forget that it's just for fun and not to take it too seriously!