LiveArea is NGP's "game-oriented communication platform," according to Sony. In other words, it's the device's (touch-controlled!) user interface -- apparently replacing the XMB -- featuring access to the PlayStation Store, Trophies, PSN friends, messaging, the browser, and other applications.
Each game will have some form of LiveArea presence, too, apparently keeping you up to date on news and even its other players (in case you bore of simply playing the game).
Additionally, LiveArea will include the "Near" feature that tracks your location over time and creates a map of where you've been. (That's not creepy at all!) Read more about it here.