Indian cuisine is a huge topic. The topic itself has similarities to that of China with many food traditions being introduced into the "cuisine of India" with a loose common thread. Noticeably the thread is that of the various Masalas.
To the casual diner, the foods of the various regions seem similar but to the native it's almost as if there is no connection or more likely broken connections. Regional differences are huge and it's a fantastic journey to explore the regional food differences and bring in the reasons and history.