Seitan probably has a Chinese origin, but notwithstanding that, the name is a Japanese word, meaning protein. In fact, it is also known as Wheat gluten, and is a high-protein food made precisely from gluten, the wheat protein.
Seitan is used to replace traditional proteins coming from animals. That’s why it is so used bu vegetarian and vegan people.
The proceeding to make Seitan is quite simple, but long too. Anyway, once the wheat protein has been obtained, it is cooked and then seasoned with soy sauce, salt and herbs, sometimes used to give it a taste similar to meat. Then it is rinsed and let to dry. The final appearance looks kind of like meat, for color and texture. In fact, it is often modelled to look like steaks, sausages, hamburgers, etc. You can cook it in different ways, usually the same you use to cook meat.