Some may think that all Indian foods are the same but there is such distinction between Southern and Northern Indian food. There are different bread and curries that you will find on the Northern side of India. This means that most of the food that you will find I Indian restaurants may come from the north.
Expect that you will see a lot of roti, naan bread, and so much more. In the South, you will see that there are a lot of stews rice, lentils, and a lot of other things. One of the ingredients that are normally used in the south is tamarind because they like a lot of sour stuff.