The following is a question and answer from the Moms Who Blog discussion group. (You can join that group by clicking the link in the sidebar. And you don't really have to be a mom to join—it's just a place to discuss blog-related topics.)
My answer here is unpolished, so if any of the other MWB contributors wants to chime in with more info, feel free to hijack this post!
A reader asked for an explanation of blog-readers like Bloglines and Google Reader. Here is my response:
A reader (also called a feed reader) makes it easier to keep up with multiple blogs. Let's say there are 40 blogs you really really like and try to read on a regular basis. (That sounds like a lot, but I think I actually have something like 300 blogs in my list! Yikes!)
You can read them by clicking on each blog individually, through your browser bookmarks or whatever, OR you can use a feed reader to see what blogs have been updated since your last visit.
Google Reader and Bloglines are the two most popular readers. I've used both—I like Google Reader the best, so I'll use it for this example. Bloglines works pretty much the same way, though.
You create your Google Reader account (or sign in with your gmail address) and then you'll need to "subscribe" to the blogs you like to read. Each blog publishes something called a "feed"—this means the text (and sometimes images) of the blog's posts gets fed to the readers.
Most blogs have a button you can click to "subscribe to my feed" or it will say RSS feed, something like that.
Or—even easier—from the Google Reader screen, you can drag a "Subscribe" button to your browser's toolbar. Then, when you're on a blog you want to subscribe to, just click that button and it'll be added to your Google Reader subscriptions.
You can set up folders or categories to organize your blogs—I have folders for homeschooling blogs, kidlitosphere, politics, food, close friends, crafts, frugal blogs, and miscellaneous.
Once you've subbed to your favorite blogs, you just go to your reader and you'll see a list of all the blogs with new posts since your last visit. If you click on the blog name, the posts will appear. Some blogs publish their entire posts to the feed readers; others publish excerpts only, and you have to click over to the blog to finish reading the post. (Full feeds are much more convenient for the readers, of course, but that does affect the blog's page views since you don't have as many people clicking onto the blog itself. I publish a full feed for Bonny Glen, but for Lilting House I have to publish excerpts only.)
There are other handy tricks you can do with your reader, such as Google Reader's nifty "Shared Items" feature (see my shared items here, for example), but their main purpose is just to pull all your blogs into one place for easy reading.