If you don’t already know, here is a cool feature that WordPress supports, it can create multiple sites using one single WordPress installation instance. Meaning that a domain owner can, technically, install WordPress once and thereby create an infinite number of sites based on that single installation. When creating multiple sites with WordPress, it presents two options, either create multiple sites within sub directories of the parent domain or multiple sites directed to different sub domains derived from the parent domain.
So why would a web design project require multisite capability anyway, well the great thing about WordPress is it has a huge amount of themes and plugins that can be installed to offer better features and functionality on a website. Unfortunately, however, this is also the main reason why WordPress websites tend to break, if and when incompatible plugins or updates are installed. The solution to this problem is to create a test site using the multisite option, where new plugins or themes can be tested, perfected and then rolled out to the main site when ready.
Another use case scenario would be to offer different services within the same website at each of the different sub domains or sub directories created by WordPress multisite. WordPress can install different themes and plugins in each individual site accordingly, giving each site a unique look and feel or catering to a different service offering enabled by a particular WordPress plugin or theme installed for a specific purpose.
There are also plugins that give WordPress multisite domain owners the ability to offer multisite sub domains or sub directories to external clients, who would be able to create their own websites as a sub-site of the parent domain, these clients can then be monetized by a pricing plan. Domain mapping plugins enable any custom domain to point towards an individual WordPress website hosted on a multisite network, therefore any visitors to the website would be unaware of the fact that it is hosted on a network of sites. WordPress multisite also gives marketers the ability to collect better segmented analytics data as well as facilitate efficient marketing automation workflows.
So the question is, if WordPress multisite is such a super feature why is it not configured into the standard install and why is everybody not using it, well firstly it is a little bit more complicated to install and update. Secondly, it takes more technical expertise to administrate multiple sites on a single network. Finally, and most importantly, what must be remembered is that WordPress shares the same database across its multisite installation meaning the single instance of WordPress will surely hit the web hosting accounts single database limitation pretty quickly especially in a shared hosting environment.