An SM file is a song file that can be loaded by StepMania. It includes descriptive information about the song and references to the music file and the images displayed during the song.
StepMania is a dance and rhythm game similar to Dance Dance Revolution (DDR). It is available for Mac, Windows, and Unix systems and supports various dance pads. Players load song files into StepMania and dance to the patterns displayed on the screen while the song plays. The program also includes a step editor, which allows players to create their own danceable song files.