Is a style of samba developed in the late 1950s and early 1960s in Rio de Janeiro, Brazil. It is mainly characterized by "different beat" that altered the harmonies with the introduction of unconventional chords and an innovative syncopation of traditional samba from a single rhythmic division. Therefore, the "bossa nova beat", then, is characteristic of a samba style and not of an autonomous genre.

Fonte: Wikepedia

https://en.wikipedia.org/wiki/Bossa_nova