The first two measures of Mozart's Sonata XI, which indicates the tempo as "Andante grazioso" and a modern editor's metronome marking: "♪ = 120".

Tempo (Italian for 'time, movement') is the speed of a song or piece of music. It is measured in beats per minute, or BPM. For example, if a song has 4 beats per bar at 100 BPM, there will be 25 bars per minute.