Mustard seeds are used a lot in Indian and Sri Lankan cuisine. They can be white, brown or black, depending on what kind of mustard plant they come from.
In India the black ones they use for vegetable dishes, the brown ones for meat dishes. Usually they are roasted on oil first, then other spices are added. It is important to heat oil on high temperature before adding the seeds. As in low temperature they woudln`t crack, which means you will not get much flavour of them into your dish.
Recipes with mustard seeds and mustard powder.