RSS stands for Really Simple Sydication and is, basically, a way to gather information from a website without having to actually access the site through your browser. For a plain english explanation of RSS, check out this video.
RSS is really helpful for collecting news or blog articles or keeping up with breaking developments because you don’t have to visit 10 different websites, all the content is brought to you through your RSS reader.
In Jumpchart you can subscribe to three different RSS feeds. The global feed consists of all updates across all your projects. When anyone changes anything this feed will let you know. The Global comments feed is composed of all the comments that are made on any of your projects. This is a great way to be alerted when a client comments on part of your Jumpchart. The last feed is a project specific feed. This feed is just like the global feed, in that you are alerted to all changes and comments, but it is only for a specific project.
There are many applications (readers) that let you collect and read RSS feeds.