The following outlines the purpose of the top-level folder structure of the Joomla Platform as found in the Github repository.

/build contains information relevant for building code style reports about the platform. Output from various automated processes may also end up in this folder.

/docs contain developer manuals in DocBook format.

/libraries contains all the server-side PHP code used in the Joomla Platform API.

/media contains any client-side resources used by the platform.

/tests contains all of the unit tests used for quality control.