Also known as carom seeds and similar to caraway , the plant is called bishop's weed.
I love using ajwain in cooking. It has to be used sparingly but really adds another dimension to the flavours. Used in savoury dishes like breads and pastry snacks I find that fish pakoras in particular are not the same without this magic spice. Try adding a bit to any white sauce for a fish dish or in a stir fry - it does not have to be a curry.