Ranch dressing is the pale, creamy buttermilk-and-herb dressing that is the best-selling salad dressing and dip in the United States and a genuine cultural staple. Built on a tangy base of buttermilk, mayonnaise and often sour cream, seasoned with garlic, onion, dill, chives, parsley and black pepper, it is at once cool, herby, garlicky and rich, and is used far beyond salad — as a dip for raw vegetables, chicken wings, pizza and fries.