Hi ansar shaik
Run modes allow you to tune your AEM instance for a specific purpose; for example author or publish, test, development, intranet or others.
You can:
Define collections of configuration parameters for each run mode.
A basic set of configuration parameters is applied for all run modes, you can then tune additional sets to the purpose of your specific environment. These are applied as required.
Define additional bundles to be installed for a particular mode.
All settings and definitions are stored in the one repository and activated by setting the Run Mode.
Link:- https://docs.adobe.com/docs/en/cq/5-6-1/deploying/configure_runmodes.html
Apart from what Praveen has mentioned there are few more article to be used as a reference.
Please find below the link for the same :
Link:- http://www.wemblog.com/2012/01/how-to-set-up-run-mode-in-cq-wem.html
Link:- http://wemcode.wemblog.com/check-run-mode
I hope this would help you.
Thanks and Regards
Kautuk Sahni
Kautuk Sahni