An excerpt from "The Food of India: a journey for food lovers", recipes by Priya Wickramsinghe and Carol Selva Rajah...
"Indian Food Myths"The type of Indian food found in the majority of Indian restaurants is based on a very successful menu formula. The original versions of these restaurants were run by Punjabis in India where they served a mixture of Punjabi cuisine, such as tandoori, and Moghul dishes such as korma and biryani. As the popularity of the cuisine grew, the 'menu' was established, then replicated in new restaurants. This menu represents a tiny section of Indian cuisine.
In India, there is no such thing as a curry. The word is of English origin, based on the Tamil word 'kari' meaning black pepper, and is a term used to denote all kinds of Indian dishes, particularly those in a sauce. Dishes in India are named either for the combination of spices used (rogan josh), for the cooking method (korma, biryani, do piaza), or for their main ingredient (saag, aloo gobi). Curry powder does not exist within India, the closest equivalent being masala (spice mix). There are hundreds of masala combinations. In northern India, they tend to be dry mixtures using ground spices such as garam masala and in the southern areas, wet ones, such as coconut masala, using fresh spices. Indian food is not universally hot. Some dishes contain lots of chillies, others none at all.