concrete5 is a Content Management System, like Joomla or Drupal
Conceived and first developed in 2003, Concrete CMS has been the glue behind many web applications, websites, stores and forums over the years. Concrete has allowed individuals involved in these websites to easily manage their content and their site structure. Concrete's in-context editing is like working a wiki, and the extendable block support makes editing and extending unique websites easy.
The goal behind Concrete CMS was always to create make it easy for anyone to run a website. In 2008 Concrete's 5th major version release was rebranded concrete5(tm) and launched fully Open Source under the MIT license.
concrete5 is also a Framework like CakePHP, Symfony or Code Igniter
While Concrete's ease of use is attractive to those who edit their website on a daily basis, the flexibility behind the framework is appealing to developers. It's all written in Object Oriented PHP 5, and follows a very extendable Model View Controller approach.
concrete5 is also a DIY site builder
We certainly designed concrete5 as a toolbox for agencies to use in building great sites they wanted to put in the hands of clients. That being said we've been pleasantly surprised over the years to see many thousands of individuals with little to no technical background have great success building a small site with concrete5 on their own - no coding required.