The method of playing jazz music that makes it different from most other types. Instead of the two eighth notes of a quarter note being equal, the first gets two-thirds the value, and the second gets the remaining one third.
Also, the second eighth note is usually accented, giving it an upbeat feeling.
It can be perceived as being doo-doo-la, with the second "doo" being weak, and the "la" being accented, at least according to my music teacher.