Impersonation means pretending to be someone else. Imagine your friend pretending to be a superhero like Spiderman or Wonder Woman. They may wear a costume and act like they have superpowers. This is like impersonation.
Impersonation in real life can be more serious. Someone may try to pretend to be someone important, like a police officer or a doctor. This can be dangerous because people might believe them and do what they say even if it's not the right thing.
It's important to always make sure we know who we're talking to and not believe someone just because they say they're someone else. We should also never pretend to be someone else ourselves, because it's not honest and can lead to problems.