FIT and GPX are two different GPS data file formats. FIT stands for Flexible and Interoperable Data Transfer and is used to store distance, date, time, location, burned calories, heart rate, speed, and other information. It is specifically used while using a GPS device during activities like running, bike racing, cycling, swimming, etc. On the other hand, GPX (GPS eXchange Format) file format is a standard GPS file format that contains waypoints, routes, and tracks.