A WordPress multisite lets you run and manage multiple WordPress sites using a single WordPress installation. You can create and manage new sites instantly and manage them using the same name and password. You can even allow people to sign up and create their own blogs under your own domain.
The advantage of using a multisite network that you can administer multiple sites from a single dashboard easily. You can install plugins and themes on multiple sites with just one download, and it is easier to manage updates.
However, using a multisite network means that you are sharing the same resources on all your sites. When one site is down, all sites on your network will also experience the same problem. Another issue is when you are just starting out, managing resources can be a bit difficult, and if your site gets hacked, then all sites on your network will get hacked too.
So you think you can handle a multisite network? Then, let’s get started: http://www.wpbeginner.com/wp-tutorials/how-to-install-and-setup-wordpress-multisite-network/