Laughter is the most enjoyable form of human communication. Humans are the only animals able to appreciate all the shadings of humor; it integrates the limbic system with the frontal lobes. (Donahue, Phil. The Human Animal. p 331-334. NY: Simon & Schuster, 1985, 1986.)
Laughter can be subcategorised into various groupings depending upon the extent and pitch of the laughter: giggles, chortles, chuckles, hoots, cackles, sniggers, and guffaws are all types of laughter. Smiling is a mild silent form of laughing.