RSS stands for Rich Site Summary (or Really Simple Syndication, take your pick). In a nutshell, RSS is a new way for people who publish content online to notify people interested in that content whenever fresh content is made available online.
There's two ways of looking at RSS: from a user's perspective, and from a technical/publisher's perspective.
As I meander around the web, I see all sorts of interesting sites, and I bookmark them - and I never look at them again, because my bookmarks are mostly things I just might need to refer to later, and all these things drown out the interesting sites that I really mean to visit routinely. So basically I end up having just a mental bookmark list of URLs that I just type in when I have some time to kill. Theonion.com, booktv.org, use.perl.org, bookslut.com, but not many others, because I just don't remember things well. And even if I did, most of the time there's not much new content at any particular site, and I have to weed thru all the old stuff to find the new stuff.
But with RSS, besides bookmarking a site, I also see its little RSS
button (altho it may be labelled "XML" or "Syndicate"), and copy the
URL of the RSS feed that it points to. I save that URL in my RSS
reader (which is effectively built into my browser -- altho it may be
implemented is a my-eyes-only/custom web
page, or as an applet or plugin that runs in my browser and saves
data locally, and occasionally may actually be a separate program).
From then on, when I have some time to kill and want to see
something interesting, I just run my RSS reader, and it starts up and
reads a dozen feeds (since they're all such small files, it happens
quickly). It then shows me a list of what's new and where.
But this works only if there's an RSS feed for sites I'm interested in. Sites without RSS feeds just fall out of my gnat-like attention span. Sites with RSS feeds draw me back many many times.
[Partly based on this, by Amy Gahran]
From a technical perspective, an RSS feed is a small data file (typically under 10KB) that a site (or subsection of a site, whatever) makes available, which lists the most recent items at that site. The file is in a simple dialect of XML; the file is meant to be autogenerated from the rest of the site -- say, from the site's content-management system, or by having a little program that just reads part of an HTML page (like the site's main page) and summarizes it in RSS.
By notifying people interested in your content, as well as Web sites that collect and package content announcements (called aggregators), you are "feeding" them your content – hence the term RSS feed.
Just about everyone who publishes content online has some sort of e-mail announcement list. I do, too. Still, RSS is a great complement to e-mail announcements because it doesn't clutter people's in-boxes, it's easier to manage for recipients who get a lot of news online, it's spam-proof, and it's easier to manage than an e-mail list.
While not a lot of people know about RSS right now, it's getting popular quickly. I wouldn't be surprised if in the next couple of years RSS becomes as widely known and used as the Web and e-mail.
In order to make use of RSS feeds, you can install special RSS reader software (also called a "news reader") to display RSS feeds in a format that the average human can read, understand, and use. It's just like how Web browsers interpret and display HTML and other types of code and files.
My favorite feed reader is Newsmonkey for first-timers (it doesn't need installation -- it's a web page), and Feed Demon for more experienced users. Amphetadesk is also free and good. NetNewswire is also good (Windows and Mac, $40). Newsgator is another great feed reader -- it integrates into MS Outlook, and allows you to simply right-click on the button or link to a feed to get a drop-down menu with a "subscribe in NewsGator" option (no need to ever see the raw XML code). And there are many, many other programs.
Bloglines is a free Web-based service through which you can set up your own personal feed reader account. It's an especially easy way to start using RSS feeds, and doesn't require that you install new software -- but there are some considerations you should be aware of before you start to use it.
[Similarly, Livejournal users can just subscribe to "syndicated accounts" like homestar_rss]
When you subscribe to a feed, you tell your feed reader that you want it to periodically poll a certain site's RSS feed file. To do this, just click on the cryptic little button that says something like "XML" or "RSS" that you see on so many sites today. That will take you to the rather cryptic feed file. Then, simply grab the URL for that page and plug it into your feed reader. It's somewhat similar to bookmarking a page in your Web browser.
Then, when you want to read the news, you tell your feed reader to go out to the feeds you've subscribed to and grab their latest information. Then, your feed reader displays that information in a way that's similar to what you see on Google News -- a list of the latest headlines from each source, sorted however you prefer, sometimes with brief descriptions of the content, and always with a link to the full content on the publisher's site.
Again, this process is spam-proof! That's the main reason why I'm an RSS evangelist.
Only the feed publisher can designate what information gets into the feed, and the only information the subscriber pulls down is what the publisher put there. When you subscribe to an RSS feed, you're not giving your e-mail address to anyone, they can't send you stuff you don't want.
This is a huge deal, especially for people who currently publish or subscribe to e-mail announcement services. Spam has become so pervasive that up to 38% of all opt-in e-mail messages (stuff that people have specifically asked to receive) get blocked by spam filters. My colleague Steve Outing wrote an excellent Editor & Publisher article on this problem last August.
There are now lots of programs available that automatically create and update RSS feeds. These are standalone or built into blogging or content-management software. Many people use RSS-generator plugins/templates for common blogging software like Movable Type.
To learn more about publishing an RSS feed, here's a great RSS primer for publishers and content providers. Also useful are the RSS 2.0 specification and the RSS Validator.
One of the best things about RSS is that you can use it to note any kind of new item -- new cartoons, articles, essays, pictures, posts, documents, even new astronomical events and new RSS files.