Foursquare is a social networking app that allows users to "check in" at locations and share their location with friends. It was created in 2009 and recommends places for users to visit based on their location and interests. Businesses can partner with Foursquare to advertise special offers and promotions to users who check in. Over time, Foursquare has grown significantly, with millions of check-ins and venues listed on the platform. It provides a useful city guide for both locals and tourists to discover new places.