Some fish sauces (extracts) are made from raw fish, others from dried fish, some from only a single species; others from whatever is dredged up in the net, including some shellfish; some from whole fish, others from only the blood or viscera.
Some fish sauces contain only fish and salt, others add a variety of herbs and spices.
Fish sauce that has been only briefly fermented has a pronounced fishy taste, while extended fermentation reduces this and gives the product a nuttier, cheesier flavour
Southeast Asian fish sauce is often made from anchovies, salt and water, it is used in moderation because it is intensely flavoured. Anchovies and salt are arranged in wooden boxes to ferment and are slowly pressed, yielding the salty, fishy liquid.
The variety from Vietnam is generally called nước mắm (well known by brand names including nước mắm Phú Quốc ( Phu Quoc) and nước mắm Phan Thiết ( Phan Thiet))
Similar condiments from Thailand and Myanmar is called nam pla and ngan byar yay respectively.
In Lao/ Isan it is called nam pa, a chunkier, more aromatic version known as padaek is also used .
In Cambodia, it is known as teuk trei, of which there are a variety of sauces using fish sauce as a base .
The Indonesian semisolid fish paste trasi, the Cambodian prahok and the Malay fermented krill brick belacan or budu from liquid anchovies, are other popular variations of the same theme.
The similar Filipino version common to Indochina is called patis.
Patis is in fact the by-product of the making of a fish paste called bagoong, and is not generally consumed "as-is" on its own.
It is nearly always cooked prior to consumption (even if used as an accent to salads or other raw dishes), or used as a cooking ingredient.
Southeast Asians generally use fish sauce as a cooking sauce, although it is sometimes used as a dipping sauce as well.
There is a sweet and sour version of this sauce, which is used more commonly as a dipping sauce ( nước chấm).
In Korea, it is called aek jeot and is used as a crucial ingredient in Kimchi (usually from myul chi, or kanari, meaning anchovies), both for taste and fermentation.
Sae woo jeot (shrimp) is also popular as side sauce.