.. glossary::
:sorted:
Distribution
A *Distribution* is a package made of the Symfony2 Components, a
selection of bundles, a sensible directory structure, a default
configuration, and an optional configuration system.
Project
A *Project* is a directory composed of an Application, a set of
bundles, vendor libraries, an autoloader, and web front controller
scripts.
Application
An *Application* is a directory containing the *configuration* for a
given set of Bundles.
Bundle
A *Bundle* is a directory containing a set of files (PHP files,
stylesheets, JavaScripts, images, ...) that *implement* a single
feature (a blog, a forum, etc). In Symfony2, (*almost*) everything
lives inside a bundle. (see :ref:`page-creation-bundles`)
Front Controller
A *Front Controller* is a short PHP script that lives in the web directory
of your project. Typically, *all* requests are handled by executing
the same front controller, whose job is to bootstrap the Symfony
application.
Controller
A *controller* is a PHP function that houses all the logic necessary
to return a ``Response`` object that represents a particular page.
Typically, a route is mapped to a controller, which then uses information
from the request to process information, perform actions, and ultimately
construct and return a ``Response`` object.
Service
A *Service* is a generic term for any PHP object that performs a
specific task. A service is usually used "globally", such as a database
connection object or an object that delivers email messages. In Symfony2,
services are often configured and retrieved from the service container.
An application that has many decoupled services is said to follow
a `service-oriented architecture`_.
Service Container
A *Service Container*, also known as a *Dependency Injection Container*,
is a special object that manages the instantiation of services inside
an application. Instead of creating services directly, the developer
*trains* the service container (via configuration) on how to create
the services. The service container takes care of lazily instantiating
and injecting dependent services.
HTTP Specification
The *Http Specification* is a document that describes the Hypertext
Transfer Protocol - a set of rules laying out the classic client-server
request-response communication. The specification defines the format
used for a request and response as well as the possible HTTP headers
that each may have. For more information, read the `Http Wikipedia`_
article or the `HTTP 1.1 RFC`_.
Environment
An environment is a string (e.g. ``prod`` or ``dev``) that corresponds
to a specific set of configuration. The same application can be run
on the same machine using different configuration by running the application
in different environments. This is useful as it allows a single application
to have a ``dev`` environment built for debugging and a ``prod`` environment
that's optimized for speed.