Wikipedia explains Drupal as a “...free and open source content management framework written in PHP and distributed under the General Public License."
To understand it better, let’s break it down into sub-parts.
1. Drupal is free and open source framework, distributed under General Public License
Drupal is free to download, use and share. You don’t have to spend any money on its license. It’s an open source software which anyone can use and share (for free).
Take for example Wikipedia, it is an open source community and you can use the information, share it with your friends and even add content to it. Same goes for Drupal.
2. It’s a Content Management Framework
To understand a content management framework, let us first understand what a CMS is. CMS is a system with which non-technical people can post content on the web. With help of CMS, you can build a website.
And a Content Management Framework
CMF is the basic framework on which you can build a content management system.
Understand the difference? Not only can you build websites but you can build applications with a CMF
3. Written in PHP
PHP is server side script used to design web development. It is flexible and easy to build various systems with PHP.
4. What can you build with Drupal?
Apart from websites, one can create intra-communication applications, blog pages, facebook landing page, community platforms, and more.