Drupal is an open-source content manager (CMS) that makes it possible to build different types of sites. We use it to design community platforms, institutional sites, e-commerce sites (Drupal commerce), web apps for tablets, etc.
The latter is used extensively by large state institutions, large companies or innovative start-ups.
Drupal is an ideal CMS for quickly designing content / product listings with intelligent filters (faceted search). The Drupal Community of Contributors offers a massive library of free modules and themes. These allow to evolve an existing site by not « reinventing the wheel » in term of functionalities.
More recently, Drupal 8 (the latest version of drupal) has been completely redesigned to work with object classes. More concretely, it today welcomes in its application core all the power of the French PHP framework Symfony, a size in the global technological landscape.