The French Baroque style of playing called notes inégales [uneven notes] was very fashionable in 18th century France.
It consists in modifying the rhythm of pairs of notes written in equal note values, making the first one longer than the second one.
For example, if the beat consists of two eighth-notes, the player would play a triplet made up of a quarter note and an eighth note.
Playing notes inégales give the music a swinging, relaxed sound not unlike that of jazz or blues music.
Menuet en Rondeau, RCT 4 -- Urtext