Flatbreads are the key component of the Indian cuisine. In the north of India they are usually made from wheat flour, in the south of India from lentils and rice. Examples of North Indian flatbreads are roti, chapati and naan.
Naan is made with yeast, roti does not have any yeast and is thinner than naan. Chapati is even thinner than roti.
Naan as served in the restaurants can be plain, butter, garlic, onion and other stuffed varieties.
Here on the picture, two pieces of plain naan.