This feature is very technical and this documentation is only for technical experts.
You should be familiar with HTTP protocol as well as HTTP Headers.
Some use case might require that RDPlus web server returns one or more custom HTTP Headers in addition to the standard ones.
This feature answers this specific need.
To add your own custom HTTP Header, you need to:
RDPlus server will now respond to all queries with this custom HTTP Header in addition to the standard ones.