Symfony2 is a reusable set of standalone, decoupled, and cohesive PHP
components that solve common web development problems.
Instead of using these low-level components, you can use the ready-to-be-used
Symfony2 full-stack web framework, which is based on these components... or
you can create your very own framework. This series is about the latter.
If you just want to use the Symfony2 full-stack framework, you'd better
read its official docu...