Roti, chapathi and phulka are the same thing. It's made from unleavened flour and cooked dry. It's what people in Pakistan (don't know about India) make in their homes.
However, the word roti has become generalized and it can be used to refer to a verity of flatbreads (except paratha). In fact, in Pashto, the word 'rotai' means a meal itself and not just the bread.
Naan/tandoori roti is what you normally get from shops. It is thicker and more filling than roti/chapathi/phulka, and are baked in tandoors (clay ovens).
Naans are more versatile because you can flavor it differently. You can add sesame seeds, zeera, or even keema (minced meat) and cheese if you go to a restaurant.
The tandoori rotis in northern Pakistan and Afghanistan are thicker than the ones you get in Punjab and Sindh.
Paratha: It's cooked with unleavened dough but its mixed with oil and shallow fried. It is prepared in a way that layers are formed. The art of making a great paratha is a complex one, because each layer needs to have its distinct flavor and texture, and it retains its softness even when it gets cold.
Like naans, they are versatile and can be flavored in many different ways, although it is normally eaten plain.
Would be even better if I knew how to make it.
