Foursquare is a smart phone social networking app, named for but not to be confused with four square the playground game.

It is GPS-based and will list venues near your physical location. You can also search for venues by name and it returns the closest matches to you physically.

When you choose a location, you “check in”, which earns you points. The app lets you see who else has checked in at that location recently, and who the mayor -- the person with the most check-ins at that location -- is. Some venues buy advertising with foursquare and offer a special for check-ins, or for the mayor.

You can also leave notes about locations, see where your friends have checked in, and earn badges for completing various tasks. Badges include ones for total number of check-ins, check-ins in a day, or special check-ins like “I’m on a boat!”.