This document discusses WordPress Multisite, which allows multiple WordPress sites to run under a single installation. It covers the advantages like shared plugins and themes, easy upgrades. Setup involves enabling multisite in wp-config.php and choosing subdomains or subfolders. Roles include Super Admin for full control and Site Admin. Plugins are recommended like Domain Mapping and New Blog Defaults. Examples given are WordPress.com blogs, Baruch College sites, and DiscoverWP.