It's a password that allows access to email, but not to the "change my Google password" page, or to push app installation to the Play Store, or to invite other

It's a password that allows access to email, but not to the "change my Google password" page, or to push app installation to the Play Store, or to invite other people into Google Meet links. These passwords are contained to very specific APIs surrounding email and Caldav and such. That means you're not completely screwed when your Outlook password database gets stolen by malware. As a user, it also allows you to revoke an application remotely without having to change your password and log in to every device again. One click of a button and new emails won't appear on a lost laptop or phone, even if they manage to bypass the screen lock. It's all about risk management.