Triple meter

Triple metre (or triple meter, also known as triple time) is a musical metre characterized by a primary division of 3 beats to the bar, usually indicated by 3 (simple) or 9 (compound) in the upper figure of the time signature, with 3
4, 3
2, and 3
8 being the most common examples. The upper figure being divisible by three does not of itself indicate triple metre; for example, a time signature of 6
8 usually indicates compound duple metre, and similarly 12
8 usually indicates compound quadruple.

It is reasonably common in ballads and classical music but much less so in traditions such as rock & roll and jazz. The most common time in rock, blues, country, funk, and pop is quadruple. Although jazz writing has become more adventurous since Dave Brubeck's seminal Time Out, the majority of jazz and jazz standards are still in straight quadruple time. One noteworthy example of a jazz classic that employs triple-meter time is John Coltrane's version of My Favorite Things.

...
Wikipedia