- ACL (Access Control List):
- Joomla's ACL offers a way of securing content and "controlling access" to certain objects and functions within a website. There are two aspects to the ACL in Joomla, who can view things and who can do things in regards to content and various actions available to users.
Joomla's Access Control List determines things like who can see certain articles and other media published on a website as well as who can add and edit content and media. It also determines who can access the Administrator and what they can see and do while they are logged in.

The Joomla Access Control List feature allows site owners to place users into groups and those groups can be given permissions as to who can create and manage content. This post explains the different actions that groups can perform.
The Joomla ACL provides two main functions; it can restrict who can view certain content and who can take action on content items, for example create an article. This post explains the basic steps for the first part - how to restrict which users can view content.