Rhythm video games are played while listening to music or a drum beat of some kind. To progress well you have to press buttons and interest in time with the music. Sometimes this is simply to make music in its own right, while at others it's to interact in others ways, often called Rhythm Action.
Many rhythm games include multiplayer modes in which players compete for the highest score or cooperate as a simulated musical ensemble. Along with gamepads, specialised input devices (plastic instruments, dance mats and the like) enable a more creative interaction.
The Rhythm interaction can be combined with all manner of other genres. This adds another later to Platform, Adventure or Shooting games. In these instances, hitting buttons in time with the beat offers additional effects or powered-up attacks. The Rhythm nature of these video games can also add an Active aspect to play. Not only do you find yourself moving your body in time with the beat to get the right timing, but some of these games offer a fully active dance experience where motion and gestures are detected by controllers.