Our PC contains many important files. It has our confidential documents, photos, videos, running projects and many important things. So, for the sake of protecting all the data, we put login password in Windows. If someone wants to access your user account, he should have the password else, he can login as different user in Windows which protects the personal files and data available in your user account.

Windows also considers password protection an important feature which is why with every new version of Windows, it made the login more secure. While this feature is essential, it becomes troublesome if you happen to forget your Windows password. Without Windows login password, you are blocked at the login screen, you can’t access your hard-disk or run any program like Google Chrome, Calculator, Microsoft Word, etc
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Do you need to sign in to your Windows 10 PC and realize that you’ve forgotten your password? Don’t panic; Windows 10 lets you reset a forgotten password, whether you use a Microsoft Account or a local account.

https://www.novabach.com/how-to-reset-a-forgotten-windows-10-password/