The experts warn against reusing passwords and writing those passwords down anywhere that an attacker might find them. Oh, yes, they add that you should change each of your passwords frequently. On this topic Newsletters Security Strategies. Administrative and support costs can be significantly reduced when users have only one password to forget, and the overall environment can be made more secure.
Authorization comes after the user is authenticated and tries to access the system resources.
The user may be authorized to view files but not to delete or modify them. The system responds to unauthorized requests with an error message and responds to authorized requests by allowing the desired access. The actual authorization might happen immediately after authentication, with the client getting a list of authorized resources. Or the authorization might be interactive, with the server denying or allowing access to individual resources when a user first tries to access them. In technical terms, SSO lets a user log on to a primary domain but have access to other, secondary domains.