Code review is like having someone look over your drawing to make sure it's really good. When you write code, you're telling the computer what to do. Sometimes, you make mistakes or leave things out by accident. Code review is when someone else looks at your code to check for those mistakes and make sure it all works correctly.
Think of it like your teacher checking your homework. They make sure you did everything you were supposed to do and that you didn't make any mistakes. Code review is kinda like that, but instead of homework, it's your computer code.
It's important to review your code because it can help you catch problems before they become too big, and you can learn from any mistakes or feedback you receive. It's a way to make sure your code is the best it can be before you use it for really important things.