The configuration module suggests best matching configuration settings based on your system setup.
Alternatively TYPO3 can 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 AdditionalConfiguration.php file or TypoScript configuration to customize settings accordingly.
Changed values are written to LocalConfiguration.php. The optional file AdditionalConfiguration.php is not controlled by the TYPO3 CMS core and may override single settings again. Administrators must maintain AdditionalConfiguration.php on their own and should use it with care.