Right now, there is a massive flap occurring in the blogosphere which is known as "Mobilegeddon". Google is going to increase the relative ranking of pages which are available in both desktop and mobile themes, as opposed to only one or the other. This has got a lot of incompetent amateurs worried about whether their sites will vanish off the search landscape, but any Drupal (or other adequate CMS) user can solve this problem with a few clicks.
A Content Management System or "CMS" allows you to develop content, while maintaining the site's infrastructure and decorations.
Drupal is an open source content management platform powering millions of websites and applications. It’s built, used, and supported by an active and diverse community of people around the world.