From the Google blog:
People tell us all that time that they’re getting more and more mail and often feel overwhelmed by it all. We know what you mean—here at Google we run on email. Our inboxes are slammed with hundreds, sometimes thousands of messages a day—mail from colleagues, from lists, about appointments and automated mail that’s often not important. It’s time-consuming to figure out what needs to be read and what needs a reply. Today, we’re happy to introduce Priority Inbox (in beta)—an experimental new way of taking on information overload in Gmail.
Gmail has always been pretty good at filtering junk mail into the “spam” folder. But today, in addition to spam, people get a lot of mail that isn’t outright junk but isn’t very important—bologna, or “bacn.” So we’ve evolved Gmail’s filter to address this problem and extended it to not only classify outright spam, but also to help users separate this “bologna” from the important stuff. In a way, Priority Inbox is like your personal assistant, helping you focus on the messages that matter without requiring you to set up complex rules.
You can learn more about how this works and how to get started using it in the full post.