If you run a company with regional offices, for instance, you might want to enable each office to have their own site, with their own pages, blogs, users and settings. WordPress Multisite enables you to do all of this, while still having a single WordPress installation at the core. It’s a lot easier to manage than having multiple individual WordPress installations.
Multisite installations have a unique user role called a super admin. Super admins can create and delete sites in the network, and they also have full access to all content and settings across all sites in the network. On multisite installations, users with the administrator role can only manage sites they’re given access to by the super admin. They also have slightly diminished capabilities compared to administrators on regular WordPress installations. They can’t install new plugins or themes, or edit others user profiles, for instance.
Sites in a network installation can have two different URL structures:
Each individual site in a network functions pretty much the same as a regular WordPress site, with their own posts, pages and users. Themes and plugins are shared across all sites in the network, although you can give site administrators the ability to activate or deactivate certain plugins.