Statamic (and Laravel) have many config files in the config
directory. Each file/directory is the 'key' to retrieve its data.
For example, if you want to check whether the Control Panel is enabled, you could use:
{{ config:statamic:cp:enabled }}
{{ config('statamic.cp.enabled') }}
To retrieve from the config/app.php
you would:
{{ config:app:variable_you_want }}
{{ config('statamic.app.variable_you_want') }}