Run modes allow you to tune your AEM instance for a specific purpose; for example author or publish, test, development, intranet or others.
Exampe: For dev: sling.run.modes=author,dev
use of run mode is, example - i have a config.author.prod and config.author.dev in crxd/e. Based on the run mode instance, the OSGI Bundle will pick the corresponding config.author.dev or prod configuration settings defined in nt:unstructured and start working.
Ref: https://docs.adobe.com/docs/en/cq/5-6-1/deploying/configure_runmodes.html
Ref: https://helpx.adobe.com/experience-manager/kb/RunModeDependentConfigAndInstall.html
Define a respository-based configuration for a single instance
There are two ways to configure CQ5.
Configure the Apache Felix Web Management Console
The configuration on the Apache Felix Web Management Console (http://:/system/console/configMgr) is always specific for the current instance.
You can find a description in the documentation: http://dev.day.com/content/docs/v5_2/html-resources/cq5_guide_system_administrator/ch05s03.html
Repository-based configuration
It is also possible to store configuration in the CRX repository as nodes of nodetype sling:OsgiConfig.
For more information, see http://dev.day.com/content/docs/v5_2/html-resources/cq5_guide_system_administrator/ch05s02.html
With this method, it is possible to share configuration among several instances.
The name of these nodes must be equal to the Persistent Identity (PID) of the configuration (for example, the name of the service). If you look at http://:/system/console/config, you see these names listed as service.pid properties. These configuration nodes have to be child-nodes of nodetype nt:folder with a name starting with config followed with a dot. All the run-modes that the config applies to are also separated with a dot.
Examples: config.author, config.publish, config.author.dev, config.author.foo.dev, and so on.