Okay kiddo, so when you play a video game, you usually control someone in the game, right? That person you control is called the player character.
Think of the player character as your own personal avatar in the game. Just like how you pick out your own clothes and hairstyle to look a certain way, you also get to choose how your player character looks and acts in the game.
As you play the game, you can make your player character stronger and learn new abilities, just like how you learn new things as you grow up. You might even get to make choices that will affect the story of the game, kind of like how you make choices in your own life.
So, the player character is basically the main character in the game that you get to control and make decisions for. Cool, huh?