The seed of the S. albis plant [a brassica relative of broccoli, cabbage, and radishes] produces the most common of the mustards and provide the most mild flavor used to make classic table mustard. When dry, yellow mustard seed is as bland as cornstarch - but mixed with cool water, its pungency emerges. For a sharper, hotter flavor, try brown or black mustard [seed or ground].
The electric yellow condiment used on most American hot dogs is made from yellow mustard seeds. Yellow mustard seed is essential to pickling spice mixes, in sausage making, and in boiled vegetable dishes, such as cabbage. Yellow mustard also combines well with other "warm" spices such as peppers and chiles.
Yellow mustard adds flavor to sauces, especially hollandaise, to dressings, and mayonnaise. In the Caribbean, mustard is used in sauces for fruit, and in India, mustard seed is toasted [dry or in oil] before adding to chutneys, curry, or sauces.