If you follow any blogs, you may occasionally see terms like subscribe, RSS, Atom, and feed reader, but aren't really sure what they mean. This post will explain a little about these concepts and show you how to use them.
RSS stands for "Real Simple Syndication." All it is is a file format that converts the content on blogs and news sites into a "feed" that can be pushed out to anyone who signs up (subscribes) to receive it. Atom is a different file format that does the same thing as RSS. As a consumer of the content, you don't need to know any more than that, which is good, because I don't have the technical knowledge to explain them in more detail. :)
A feed reader is an application that receives the feed and displays the content of it. Because a feed is automatically updated whenever new content is added, a feed reader is a convenient way to follow a blog without always having to go back to it to see if there have been any new entries since you last visited. There are many feed readers available, but here are a few popular ones. You can see that each one has its own way to display the content (I'm using the Tech for Luddites feed as the example).
Note: Depending on which browser is being used and what settings have been applied to the feed reader, the results may look different from the screenshots below.
My Yahoo
If you use My Yahoo to track news stories, you've been using a feed reader all along, even if you weren't aware of it. All those headlines in the Top Stories, Business News, and other modules are being pulled in by various feeds.
Google Reader
This is one of many applications you can access when you create an account with Google.
Bloglines
Unlike My Yahoo and Google, which offer a wide variety of services, Bloglines is primarily a feed reader.
Outlook 2007
The latest version of Outlook has a feed reader built into it. I described how it can be used to track Twitter topics of interest in an earlier post.
Another advantage of a feed reader is that you can keep track of multiple feeds in a single location. So, for example, if you want to follow a dozen blogs, you don't have to keep going back to each one individually—you'll be alerted whenever new content is added. Depending on how the blog publisher has set up the feed, you may see the full text of the posts in the reader or you may just see the headline and a short excerpt and then have to click a link to read the full piece on the actual blog.
Which feed reader you use will simply depend on personal preference, so you may want to test out a few to see which one appeals to you the most. And there's no reason you can't use more than one. For example, if you check My Yahoo regularly anyway, you might want to add the feeds for the blogs you read the most to it, but then use a different reader, like Bloglines, to keep track of additional blogs that you enjoy, but don't feel the need to follow every day.
Subscribing to a Feed
When you find a blog or a news site that you would like to keep track of, you'll want to "subscribe" to it, using your feed reader(s) of choice. 
Most sites that generate a feed will have a link on it that will make it easy to set up the subscription. For example, in the right-hand sidebar of T4L, you see the link at right.
Note: The orange icon is a standard image that sites use to indicate there is a feed available, so looking for that can help you quickly find a subscription link if it's available.
When you click the link, you'll be brought to a page that shows you what the current items are in the feed and that offers you a choice of feed readers to use to subscribe to it. You'll see the URL for the feed in the browser location bar.
Depending on how the feed is set up, the page may look different. For example, here are a couple of different examples you might see.
From here, you can just select the reader you want to use, and it will either automatically add the feed to it or ask you to choose some options first. If you don't already have an account with the reader service, you'll be prompted to sign up for one as well.
Once you have a certain reader set up, you can subscribe to blogs directly from within it as well. However, since each one has its own steps, I'm not going to cover those at this point.
Instructions for Outlook 2007
Because Outlook isn't a web-based service, it won't always appear in the list of readers to choose from on the Subscribe page. If you want to use it as your feed reader, follow the steps from my earlier post (link below) and simply replace the Twitter feed URL with the one for the current blog's feed.
Keep Track of Twitter Topics in Outlook 2007
