What is "notes inegales"

In music, notes inégales (French: unequal notes) refers to a performance practice, mainly from the Baroque and Classical music eras, in which some notes with equal written time values are performed with unequal durations, usually as alternating long and short. The practice was especially prevalent in France in the 17th and 18th centuries, with appearances in other European countries at the same time; and it reappeared as the standard performance practice in the 20th century in jazz.