Authentication is the process of confirming an identity. Authorization means granting access to a restricted resource to an identity, and access control mechanisms enforce these restrictions. Authentication and authorization can be enforced by a number of security models (Web application security, htaccess, Authentication Realm and more) and services.
Who can access your Administration Server
Which applications they can access
Who can access the files or directories on your web site
You can control access to the entire server or to parts of the server, or the files or directories on your web site. You create a hierarchy of rules called access control entries (ACEs) to allow or deny access. The collection of ACEs you create is called an access control list (ACL).
By default, the server has one ACL file that contains multiple ACLs. After determining the virtual server to use for an incoming request, the server checks if any ACLs are configured for that virtual server. If ACLs are found that apply for the current request, the server evaluates their ACEs to determine whether access should be granted or denied.
You allow or deny access based on: