It should have small chunks of each ingredient rather than being a homogeneous liquid. The taste is sour and hot, very puckery. It's great with poached or steamed chicken, duck or game hens. Good with Chinese white-cut chicken or Steamed Ginger Chicken with Black Bean sauce. Should be good with a firm- fleshed white fish or boiled shrimp or crab.
Fish sauce is a liquid made with anchovies and salt.
It's not really fishy tasting. Look for it in the oriental section of supermarkets or at markets catering to Asian clientele. Tiparos is a good brand made in the Philippines. I prefer Thai or Vietnamese fish sauce, but they'll probably be harder to find. A timesaver is to combine large quantities of the liquid ingredients and store them in the fridge.