Not strictly a curry but more of a stew or chowder. Made with vegetables, lentils and a broth of tamarind and pigeon peas. This dish is popular in southern India, however you would be unlikely to find this as a stew on a curry house menu in the U.K. It is more likely that you will find a curry variation of the traditional Indian dish.
In India, sambar is served with steamed rice, and variations of the dish are eaten for breakfast and lunch.