You mean "RSS Reader"?
An RSS Reader is a tool for downloading content (typically news or discussions) from a website into a reader especially designed for reading, instead of relying on whatever controls a web designer was able to put into your web browser. Since the software is specifically written for reading news and discussions, it is a far superior experience to anything that can be achieved with a web browser.
Unfortunately, as far as I know, no RSS readers allow you to post, as yet. However, I'm not sure.
Incidently, as far as I know, The DIS does not support RSS, but vBulletin, the server software The DIS uses, does support it.