It doesn't matter what you call it, fish sauce, nuoc mam, patis, or nam pla. It's all the same fishy goodness.
Fish sauce is made by a few varying methods, but they are all basically the same. Fish, usually anchovies and sardines, but sometimes whatever comes up in the net, are mixed with salt and maybe some water and allowed to ferment. The fermented juice that comes off is fish sauce. sometimes it is drained from the bottom and added back into to the top of the fermenter until fermentation has completed, and sometimes it isn't. There isn't much of a wrong way to make fish sauce.
Where the Chinese and Japanese use soy sauce, much of southeast Asia uses fish sauce. It has a rich savory flavor like soy sauce, but better. It is actually believed that fish sauce came first, and that soybeans were added to extend the fish sauce, until eventually the fish were left out altogether.
Fish sauce is not an entirely eastern food either. The romans had fish sauce too. They called it garum or liquamen. It was used in food, medicine, and even in cosmetics. Like so many things, they got it from the Greeks. It was usually made from just the guts of fish. Some modern fish sauce is as well.
Fish sauce can be used in place of soy sauce in many applications. It has a good umami kick to it and a nutty slightly cheesy flavor. When you first open the bottle, don't let the aroma scare you off. Its a little stinky. Supposedly when the French first got to Vietnam and tried fish sauce they described the aroma as "a young girl that does not wash properly." I had a friend that once said, "If you can get it past your nose its one of the most delicious things there is." It doesn't smell that bad. I really think people get all worked up over nothing.
so what are the health benefits of this traditional food? It has almost all the same health benefits that fish broth has. Think about it. One is boiling fish until the goodness comes out, and the other is fermenting fish until the goodness comes out. Fish sauce is high in minerals, especially if made from small fish like anchovies so the total bone content is higher. It also contains small amounts of thyroid hormones.
My favorite fish sauce recipe was posted in my "eat your heart" out post. Another great thing to use fish sauce with is vegetables of all kinds. I like to take zucchini and summer squash, brown in some butter or olive oil, then add a little fish sauce and let it cook in. Something my Stepmother does is brown some ground beef and cook it with patis(Filipino fish sauce) and chayote(AKA alligator pear). It is delciious and satisfying!
So what are you waiting for? Go buy some fish sauce! Start cooking already!