It's tangy as in potato salad; it tenderizes biscuits and chocolate cake; it's thick like cream for a great herbed marinade in chicken and fish; it is a famous salad dressing ingredient, and no, it does not contain butter.
Way back when, buttermilk was the liquid left over after the butter was churned. This liquid combined naturally with airborne bacteria to become thickened and “soured.” Today's buttermilk starts from lowfat or skim milk and is cultured with lactic acid. At 2 grams of fat per cup versus the 78 in a cup of cream.