Multisite is a type of WordPress installation that allows you to create and manage a network of multiple websites from a single WordPress dashboard. This lets you easily make changes and keep all of your websites updated from one place.
You can create a multisite network for yourself that only you have access to. Or you could add other users who can create their own sites inside your network, and limit them from accessing more powerful WordPress features.
For example, Harvard University has a WordPress multisite network called Harvard Blogs that allows anyone with a harvard.edu email address to create their own blog. Bloggers can publish blog posts on their own sites, but only the owner of the multisite, called the “super admin”, can install plugins or make other sitewide changes.
When Should You Use Multisite?
WordPress Multisite is best used when you’re creating a network of sites sharing similar functionality. Ideally, this similar functionality has been added through plugins, custom applications, or specific server configurations. It truly works best when used on a limited number of themes specifically curated for the purposes of the network, as opposed to allowing members of the network to upload their own custom themes. If your network consists of widely different WordPress sites (different in terms of plugins, themes, and customization), then multisite is not a good fit for you.
WordPress.com is, by far, is the largest example of a multisite network. Other site owners who have had success with multisite typically have a common theme (no pun intended) that ties their network of sites together and lends itself to similar functionality and themes. Universities are a great example. A lot of them use multisite to provide their staff with a way of posting internal blogs. Real estate companies are another example. They use WordPress Multisite as an easy way to provide their real estate agents with a basic website. The designs of these sites are the same, only the content is different from realtor to realtor.