Ghee is clarified butter or cream. It is used extensively in Indian cooking for sautéing, frying, shallow-frying and even deep-frying. It is also added to dough or drizzled over a cooked dish or Indian bread just before serving to give a rich, nutty, buttery taste. Because it is clarified, it can be heated to higher temperatures than butter without burning.
You can buy ready-made ghee from Indian grocery stores. In some recipes you can use salted butter as a substitute for ghee, while in other recipes you can use vegetable or canola oil instead, but they will not bring the same rich flavour to the dish.