The Configuration Module recommends configuration settings based on information found in your environments setup.

TYPO3 can also be run in a specific application context, by setting an environment variable in the web server configuration. The application context can then be accessed e.g. in the system/additional.php file or TypoScript configuration to customize settings accordingly.

Changed values are written to system/settings.php. The optional file system/additional.php is not controlled by the TYPO3’s core and may override certain settings. Administrators must maintain system/additional.php manually and should be used with caution.