What is the guest user for?

What’s the purpose of the guest user? Seems to me that guest is like any other user. The documentation seems to say that guest allows everyone to access to the web page for the purpose of inspecting host and service status without allowing them to change anything. And that’s what I want to do. But in setting it up guest requires authorization and a password just like all other users. So what’s special about guest?
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I don’t see where the docs say that at all. URL please? What I do read, is that the user guest login will have all rights that you assign to it. It is used so that people don’t have to login, and when they don’t, this is the user that is used.