Launched in March 2009, Foursquare was a free, location-based social network service for both mobile and (to a lesser extent) the web. Using the GPS hardware in the mobile device or network location via the app, registered Foursquare users could ’check in' at venues located nearby. Check-ins could be made via the mobile website, text messaging or application. Each check-in awarded the user points. Accumulating check-ins earned the user 'badges' which marked honors and achievements reached within foursquare. Checking in at a venue more than any other user in a 60-day span earned the user the title of 'Mayor' of that venue.
Then the summer of 2014 came along.
Back in May 2014, Foursquare (still free) essentially spun off the ‘check in’ and location sharing aspects of Foursquare into a new free app called Swarm, designed to be a companion app to Foursquare.
In August 2014, Foursquare released version 8.0, removing the check in and location sharing altogether, focusing solely on local search.
Foursquare now enables users to search for restaurants, nightlife, shops and other places of interest in the surrounding area where the user is located. Recommendations are personalized based on time of day, check-in history, venue ‘Ratings’ and the user’s ‘Tastes’ that they have entered into Foursquare.
Definition in part from Wikipedia, Foursquare