Near is the PS Vita's social feature that scans the area for PS Vita brethern.
To use Near, press the Update button. Your Vita will search for players nearby, and once it's found them, you can challenge them or even play co-op. Concept trailers like this have hinted at features like the ability to send and receive new levels via Near as well as unlock items.
Concept trailers have also shown how Near can be used to view other people's trophies, stats, and trophies. That way you can see if it's wise to challenge that dude on the bus or not.
PlayStation Vita Box Designs and Launch Apps [PlayStation.Blog]