The mallard is a wild bird, belonging to the family Anatidae. They usually live in water, have slender beaks and webbed feet, and can swim and dive in the water. Domestic duck is a kind of poultry domesticated by wild ducks, which is usually used as a source of meat and eggs.
Although wild ducks and domestic ducks belong to the family Anatidae, there are genetic differences between them, which prevent them from producing fertile offspring. So wild ducks and domestic ducks can't breed.