Mustard is a type of plant whose seeds are often used to create the condiment by the same name. Mustard seeds are ground finely and then combined with vinegar and sometimes other ingredients to create a wet paste. Mustard is most commonly used in sandwiches and on hot dogs, but can also be used to flavor other dishes. Mustard comes in many different types, including yellow, brown, and Dijon varieties. The mustard plants themselves are often used in vegetable dishes as well.