Fish sauce is an almost indispensable umami ingredient in South East Asia, particularly in Thailand, Vietnam, Cambodia, and the Philippines. Used properly in cooking, you are unlikely to taste it specifically in the finished dish, but it will enhance and deepen the flavours as a whole. In addition to its use in cooking, it is often used as a table sauce, particularly in combination with citrus, chiles, garlic and other aromatics. Red Boat is an all-natural, very high quality (and expensive!) version.