Authentication Method identifies the method or process in which the Authentication was performed and not the Authentication Protocol that was utilized.
Authentication Context Class Values shows the Authentication Process that was used.
Authentication Context Class vs Authentication Method Reference shows the differences between the two.
Authentication Methods that involve more than one Authentication Methods or Authentication Factors may be referred to as Multi-Factor Authentication.
Authentication Methods that involve Authentication Methods across more than one communication channels may be referred to as Multiple-channel Authentication
There are many technologies and methodologies implemented to provide authentication.