It is said tofu was invented 'by accident' over 2000 years ago in China, however, little else is known about its origins and method of production. What is known is that tofu was subsequently introduced into Japan, Korea and other parts of East and Southeast Asia and is now a widely used source of protein in the East and the West.
The easiest way to understand how tofu is made is as follows: "Cheese is to cow's milk as tofu is to soy milk"(source: sparkpeople.com, tofu101, Liz Barnes). Technically, tofu (or bean curd) is made from the soybean plant and is a soft, white food made by pressing condensed soy milk into blocks.
There are two categories of tofu: Fresh and Processed. Fresh tofu is divided into three varieties - defined by the amount of water extracted from the tofu curds: Soft, Firm and Dried. Processed tofu comes in many forms and likely originated from the need to increase the product's shelf life.
Tofu is a versatile food, as it has little flavor or smell on its own and is often seasoned or marinated to suit the recipe.
Tofu is a healthy protein source, as it is high in iron but low in calories and fat. Depending on how it's manufactured, tofu may also be high in calcium and/or magnesium.
Source: "Tofu." Wikipedia, The Free Encyclopedia. 26 Dec 2009, 03:20 UTC. 30 Dec 2009 <http://en.wikipedia.org/w/index.php?title=Tofu&oldid=334043440>.