RSS is a file format used to syndicate content. Originally used for blog, it is the underpinning technology for podcast distribution.
The index file (in RSS or ATOM standard format), lists information that is read by a feed reader application. The benefit comes from the app checking for new items instead of me needing to visit them all individually. I only have the one place to check.
There is the question, Does Your Blog Really Need to Provide an RSS Feed Anymore?. I will, and I think it should, as its the way I prefer to consume content.