Gravies and spices are the soul of Indian cooking. If you are in India and you don't taste the gravies then I would say that you haven't really visited India!
There is a common thread that runs through all Indian cooking be it from North, South, West or East - Gravies & Spices.
Secret of happiness is variety. But secret of variety like the secret of all spices is knowing when to use it …Daniel Gilbert, American Social Psychologist
Gravies are thick liquids of consistency and they lend the body & flavour to the famous curries of India which drove England crazy. It is these gravies that give the basic 5 tastes recognized by your palate - hot, bitter, sour, sweet & salty.
The rich & varied Indian cooking from different regions comprise basically gravies of following types, each different from the other in colour, flavour & spice: