Yogurt, or dahi, is an important ingredient in Indian cuisine. Dahi is Indian yogurt, and is similar in thickness to greek yogurt.
It makes an excellent accompaniment to many dishes, often as a cooling counter-flavor to spicy dishes. Yogurt goes well with rice, dal, and many vegetables.
It is easy to make a quick meal out of stuffed paratha and a simple yogurt dip. Raitas are yogurt with some spice or vegetable added.
Yogurt also makes a great base for a marinade often used for tandoori-style dishes. You can easily make yogurt at home with milk and a little bit of yogurt as a starter.