Usually, you'd activate Windows 11 (or 10) using the Settings app to enter the product key. However, if you're in an enterprise environment and you have a specific type of activation key, you can also ...

If your Windows 10 product key is not working on Windows 11, check the Windows Edition, your activation status, and then ...

Your Windows 10 product key serves as proof that you actually own Windows 10, and might need to be entered when you reinstall ...