Nam pla (Thai), Nuoc Nam (Vietnam), Nam pa, (Lao), Shottsur, (Japan) or Garum in ancient Rome. No matter what you call it fish sauce is the backbone of Asian cooking. The pale colored fish sauce is used as a condiment, in sauces or as a seasoning. The most common ingredient in Thai cooking, it is also used in many other types of Asian cuisine.
If you don't have fish sauce and need a substitute try this simple recipe. (See vegetarian version too)
Mix 1 part soy sauce with 4 parts anchovies
Combine soy sauce and sherry in a small bowl. Mash the black beans with the back of a fork and add to the soy sauce mixture. Let this sit for at least 10 minutes so that beans soften. Add miso and mix well. When ready to use, strain out solids. Store refrigerated indefinitely. Flavor intensifies over time. *Fermented black beans (soybeans) can be found in Asian markets.