Yellow mustard seeds are one of the most popular and widely used varieties of mustard. They have a pungent and spicy bite but are milder than their close relative, brown mustard seeds. Grinding the seeds will increase their pungency for a more piquant flavor. Yellow mustard seeds are an important spice in many regional foods and recipes ranging from condiments, soups, sauces, marinades, pickling blends, and rubs.