RSS Subscription
RSS stands for "Real Simple Syndication" (amongst other things, there are a few variations, but they all mean basically the same thing), what it means is that you can subscribe to a website and get sent updates when a new post or article is submitted. This means that you don't have to check every website you go to all the time, it will let you know when there is something new.
It works a little like e-mail, you need an RSS reader (I use Google Reader), which displays new posts for you to read. It allows you to read a lot of websites (when they have something interesting to say) all in the same place and a lot faster than it would normally take.
Here's a video from Common Craft called RSS in Plain English:

