Multisite is a WordPress feature which allows users to create a network of sites on a single WordPress installation. Available since WordPress version 3.0, Multisite is a continuation of WPMU or WordPress Multiuser project. WordPress MultiUser project was discontinued and its features were included into WordPress core.

WordPress Multisite Network Features:

• You can run a network of multiple WordPress blogs and websites from a single WordPress installation.
• You can have a network of subdomains like http://john.example.com or directories like http://www.example.com/john/.
• Open up your WordPress Multisite Network for other users to create an account and get their own WordPress blogs.
• As a Super Admin you can install themes and plugins and make them available to all other sites on the network. However, other site admins on the network will not have the capability to install themes or plugins.
• As Super Admin you can change make changes to themes for all websites. Website Admins cannot make changes to their themes.