What is the difference between Yoghurt and Curd
A curd is a transitional element obtained, once milk starts to coagulate, the other being a water substance called whey. These are separated and cheese can later be made from the curd, via the addition of other ingredients, such as rennet. Or in the case of cottage cheese and paneer, an acid.

Yoghurt is a finished product, produced by by heating milk, then adding a live 'starter' culture. It's then kept at a stable warm temperature for a number of hours, followed by cooling.