Back in the mists of time, the early days of RSS, there was a lot hand-wringing about how people were going to find out about a website's feeds.
On a Windows system, you can configure one program to handle http:// links when they are clicked, (e.g. Internet Explorer), another one to handle mailto:// links (your email program), etc. One of the proposed solutions was to have a new protocol called feed:// and have Windows launch your RSS program to handle it, the idea being that web sites could have a "click *here* to subscribe to our feed" and your RSS program would automatically launch to subscribe. Ticking the check box in Awasu's admin program registered Awasu as the handling program for feed:// links.
The idea never gained any traction, not enough web sites used it, and it can more or less be considered obsolete.