Taucheo are salted, fermented soy beans. They are sold in paste form, and whole, as you can see from the image above.
Taucheo is very salty and has a slightly smoky aroma and flavour. It is used in many dishes in East (China, Korea) and South East Asia (Malaysia, Singapore, etc) to deepen the flavours of dishes. Given its bold temperament, a little goes a long way.
In Korea, this is sold as a paste and known as Doenjang, which is used as both an ingredient and a condiment.
Substitute: Dark Miso Paste, Hoisin Sauce
On LinsFood, some of the dishes we use it in are: