A chafing dish (from the French chauffer, “to make warm”) is a kind of portable grate raised on a tripod, originally heated with charcoal in a brazier, and used for foods that require gentle cooking, away from the “fierce” heat of direct flames. The chafing dish could be used at table or provided with a cover for keeping food warm on a buffet. Double dishes that provide a protective water jacket are known as bains-marie and help keep delicate foods, such as fish, warm while preventing overcooking. (source)