Mustard is most often used as a condiment on meat, especially cold meats such as ham; the French like strong Dijon mustard with steak. It is also used as an ingredient in mayonnaise and vinaigrette. There are many varieties of mustard, which vary in strength and flavour. Places known for their mustard include Dijon (strong) and Meaux in France, and Norwich in the UK.
In the USA mustard is often used as a condiment in combination with ketchup. Plochman's is a popular brand in the United States.
See also: mustard gas