Pimcore supports different configurations for different environments (dev, test, stage, prod, ...) as well as custom configurations including a fallback mechanism.
Pimcore is relying on Symfony's environments, with some extras, however all the essential information can be found in the Symfony Docs
In addition to Symfony configurations, Pimcore also supports environment specific configs for:
The environment specific config file has priority over the default config, so if your
current environment is
dev Pimcore first checks if e.g.
exists, if not the default config
var/config/image-thumbnails.php is used.