The beats per minute is the number of musical beats that occur within 60 seconds of a song. Musicians use it to measure the tempo.
Beats per minute proves important to DJs because songs need to have the same tempo in order to properly mix them.
According to The Craft and Business of Songwriting, different tempos work better with different kinds of songs. Slow ballads like The Beatles' "Yesterday" and Boyz II Men's "I'll Make Love To You" have 60 beats per minute, while mid-tempo songs like Madonna's "Crazy For You and TLC's "No Scrubs" have 90 beats per minute.
Beats per minute plays an important role in distinguishing different types of electronic dance music. Trance music generally has between 130 and 155 beats per minute, while house ranges from 118 to 135 beats per minute.
Working out to music with a tempo between 120 and140 beats per minute can improve results according to a New York Times article.