Dear @Thushitha Chandrasiri
The value to be filled here is simply the application server URL where IFS is installed for any company.
For ex: https://ifstest.<ClientName>.com or https://ifssprod.<ClientName>.com/main
Where used : If there is any scenario, where mail notifications or even task notifications are being generated for a document revision, and event work flows are being configured to generated the application link which points back to the specific document, then the above definition will be useful.
Not defining it, does not break the document management solution, but useful only to ensure that system points to a usable URL.
You can only configure , the scenario and test it .
Regards
Vivek