At the heart of each loaf of bread there is gluten, the sinew-like elastic mass that develops as you knead bread dough. While all the other parts of the wheat (bran, germ, etc.), contribute the fiber and roughage, gluten contains the protein.
Seitan (coined by Japanese philosopher Georges Oshawa to mean “made of vegetable protein”) is often used as an alternative to soybean-based meat substitutes such as tofu. Some types of wheat gluten have a chewy and/or stringy texture more like that of meat than most other substitutes. Since the mid-20th century, seitan has been increasingly adopted by vegetarians in western nations as a realistic meat substitute, particularly by vegetarians who previously ate meat and miss its taste and/or texture.
One story attributes the invention of imitation meat to chefs who made it for Chinese emperors who, traditionally, observed a week of vegetarianism each year.