The Punisher is a character who appears in comic books, movies, and TV shows. He's a tough guy who fights crime using lots of guns and other weapons, and he's known for being really brutal when he takes down bad guys.
Imagine you're playing a game of cops and robbers with your friends. You're all pretending to be police officers who catch robbers and put them in jail. The Punisher is sort of like the ultimate cop in that game, but he's way more serious and intense about it. He doesn't mess around with the robbers - he doesn't just put them in jail, he tries to stop them from ever doing bad things again by punishing them.
Now, when we say punish, we don't mean a time-out or a stern talk with your parents. The Punisher beats up bad guys, or shoots them, or sets traps to catch them. He doesn't believe in giving them any second chances. Some people like the Punisher because they think he's a hero who's doing what needs to be done to rid the world of bad guys. Other people don't like the Punisher because they think he's too violent and he takes things way too far.
So, in a nutshell, the Punisher is a tough guy who fights crime in a really violent way. Some people love him, and some people don't.