This is a re-published (& slightly updated) article, orginaly published on my first blog The Journal (now offline, redirecting here)

What is RSS?

You may have seen the RSS 2.0 image on some sites, or maybe a link to “Syndicate this site” or “RSS” or something similar and wondered “What is all this talking about? Does it matter? Is it useful to me?”

Well the answer to the last two questions is ‘yes’ and ‘most probably’ respectively.
The short answer to the first question is, RSS stands for "Really Simple Syndication", "Rich Site Summary" or
"RDF Site Summary" depending on who you talk to. I prefer "Really Simple Syndication", but that’s just me. It
doesn’t really matter. Whatever you call it, this is is a way to ’syndicate’ the headlines from a website. This could be a news site, a blog or any other site that has regularly updated news or articles. Syndicating headlines means to get the latest headlines, and often a short blurb about the article & a link to the article (Newer versions of RSS actually have more information than that, but that can be discussed later).

For a long answer to the question "What is this talking about?", let me give you descriptions of RSS from two well-respected technical authors:

Mark Pilgrim writes for XML.com about RSS:

RSS is a format for syndicating news and the content of news-like sites, including major news sites like Wired, news-oriented community sites like Slashdot, and personal weblogs. But it’s not just for news. Pretty much anything that can be broken down into discrete items can be syndicated via RSS: the "recent changes" page of a wiki, a changelog of CVS checkins, even the revision history of a book. Once information about each item is in RSS format, an RSS-aware program can check the feed for changes and react to the changes in an appropriate way.

http://www.xml.com/pub/a/2002/12/18/dive-into-xml.html

or, Andrew B. King writes for webreference.com:

Rich Site Summary (RSS) is a lightweight XML format designed for sharing headlines and other Web content. Think of it as a distributable "What’s New" for your site. Originated by UserLand in 1997 and subsequently used by Netscape to fill channels for Netcenter, RSS has evolved into a popular means of sharing content between sites (including the BBC, CNET, CNN, Disney, Forbes, Motley Fool, Wired, Red Herring, Salon, Slashdot, ZDNet, and more). RSS solves a myriad of problems webmasters commonly face, such as increasing traffic, and gathering and distributing news. RSS can also be the basis for additional content distribution services.

http://www.webreference.com/authoring/languages/xml/rss/intro/index.html

RSS is basically a file that sits on a website, providing information about the content of that site. That file is referred to as an "RSS Feed" and it can be retrived & displayed by
programs to provide regularly updated information on the content of the site.

As Andrew says in the above quote, RSS is a standard written in XML.
If you don’t much about XML, check out the
tutorial on
w3schools or have a look at
XML.com.
For the technically minded out there, the specs for the different versions of RSS can be found on
blogspace here:
http://blogspace.com/rss/specs.
The most common version is RSS 1.0, but RSS 2.0 is also used & is becoming increasingly popular.

"OK, that’s nice," I hear you say "so what the heck can I do with it?". Well, I’m glad you asked, read on…

What you can do with it

The most common use for RSS is to be put into a personal aggregator that
regularly checks for updates on your favourite sites. I’ve used FeedDemon,
which I love, but there are plenty of others to choose from.

The aggregators generally run hidden in the background while you work (or play) on the computer. On a regular basis the
aggregator program checks the list of RSS files you have specified (like this site’s) for
changes. If there are changes it downloads the new text and displays the information (usually a headline, a brief description & a link to the page).

This is amazingly useful, it means that you can keep up to date with all the regular sites you visit, without having to constantly check back
to see if there are updates. You only need to go there when the aggregator tells you there is new content on the site.
This has been incorporated into google(Bulletin Boards) too, so you know when new posts have been added without having to keep reloading the site. For example the
Anglican Media Sydney Forums have an
RSS feed. I use this to know
when there is a new post on the topics I’m interested in.

Syndirella Screenshot
This is a screenshot of Syndirella (Another aggregator). On the left column is the list of RSS feeds that the you have put into Syndirella. By clicking on one of the titles there, the two right frames change to that feeds information.
The top-right frame displays the list of articles available for that feed, and the bottom-right frame shows the information on the selected article. As you can see that information can include HTML (links, images & formatted text), or it can just be plain text with a link
to the article as specified in the RSS file.

It is also possible to incorporate RSS feeds onto websites (like the Voice of the Martyrs News on this site) To find out how to do that, have a look
here for a Perl script to do just that.

Conclusion

As you can see, RSS can be very time saving & flexible. It is also good for the sites that use RSS because it drives traffic to your site. People who subscribe to your RSS feed are more likely to come back when they see that the site has new content on it.

Next time I will show how to actually build an RSS feed for your site.

Further Reading

Some RSS Feeds

Here is a list of a few common RSS Feeds

There are a number of sites & books that you can read to find out more about RSS

Websites

Books