The live, real-time stream means you won't have to hit refresh to see your latest updates and activity -- rather, the page will act as a user-controlled scrolling marquee, constantly notifying you as new information rolls in.
The service follows a real-time option just last week. There, the change has divided users, with many complaining the constantly refreshing feed .
In contrast to FriendFeed's configuration, in which live updates scroll automatically unless you hit a "pause" button, Facebook's new system will present an option for you to see incoming updates as they arrive via a top-of-page prompt. You'll have to click that notification for the new updates to appear -- something that may help cut down on motion sickness.