Drupal Multisite enables separate, independent sites to be served from a single codebase.
Drupal is a free and open-source web content management framework.
Internet Information Services (IIS) is an extensible web server software created by Microsoft for use with the Windows NT family.
PHP is a general-purpose scripting language used for web development.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.