Indian Name: Sarso, Rai
Mustard seeds are mostly used for tempering and these seeds are added into very hot oil to splutter and release the aroma.

In South India, it is typically combined with green chilies and curry leaves for tempering.
The green leaves of mustard plant is also edible. And is known as Sarso Saag, which is prepared in Eastern and North India and served as a side dish for rice or roti.
We use mustard oil to make most of the dishes, it gives a distinctive pungent taste to the vegetables and meat.
Coarsely ground mustard seeds are used to make many Indian pickles.
Mustard seed is also an integral part of Panch phoron (5 spices), a spice blend from Eastern India along with nigella seeds, cumin seeds, fennel seeds and fenugreek seeds. This is used for tempering Dals (lentils) and green leafy vegetables
How I use them:
Besides all of the above use, I use them in many different ways.
I soak and grind the mustard seeds with few cloves of garlic, and green chilies to make a fine paste.
This is called “besar”. It is used as a base to make gravies along with tomatoes or a sour ingredient. The besar gravy goes very well with vegetables like Okra, Green flat beans, Brinjal, Drum stick.
I also relish small, or big fish curries, prawns curries with this mustard paste.