Cooking ingredients

To cook any dish properly, a good introduction to the ingredients that go into it is a must. For example, when a recipe lists scallions as an ingredient, does it refer to onion leaves, or are scallions and onion leaves different from one another? What is the proper way to rehydrate dried mushrooms?  What is fish sauce and why is salt not a worthy substitute? What is shrimp paste and why is it such an important ingredient in Asian cooking? All these and more in this section.