Many navigation devices or computer programs use .trk files to store data about land tracks or routes. Hence a conversion to other exchange format for the purpose of transferring the data from one device to another (for example trk to kml conversion) is often useful. You can find special converters, such as the GPSBabel, which are excellent for this job and support huge number of various navigation formats.
Open TRK file Open KML fileProgram for Linux that allows users to convert waypoints, tracks, and routes between popular GPS receivers