Fabien Potencier of the Symfony project (framework) recently made a presentation at the Symfony Day conference and answered the question "what is Symfony2?"

When I ask people what Symfony2 is for them, most of them say something along the lines of: Symfony2 is a full-stack web framework written in PHP. Some also add that this is an MVC framework. And some others add that this is a decoupled framework. This is all fine and correct. But my definition is a bit different. Let me tell you what it is and why I think it matters. Symfony2 is really about two different things.

His "two things" are simple - first that Symfony2 is a "reusable set of standalone, decoupled, and cohesive PHP components that solve common web development problems" and second that the framework is, based on these components, a full-stack framework. He also answers a common question about the framework - is is really MVC? He explains that the framework is less about adhering to a design pattern and more about being useful as a HTTP framework (request and response). He finishes off the post with some thoughts on the framework's place in "the enterprise", innovation, reusing standard, well-tested tools and some reasons why to choose Symfony for your next project.