问题:

The term REALM has an overloaded & confusing using in security, what is the exact uses of this term in security?

回答1:

Take a look at this in-depth explanation:

Security Realm

A security realm is a mechanism used for protecting Web application resources. It gives you the ability to protect a resource with a defined security constraint and then define the user roles that can access the protected resource.

I hope this helped!

回答2:

In simple terms when you want to access a protected resource you need to identify your self with something like a username and you also need to provide something secret to prove that you are not laying, like a password (credential).

Then this information is checked against a repository and based on the information provided you will be given special privileges (these privileges are defined by the role assigned to you and the user group you are in).

The realm is that repository that does all such controlling stuff.