Wheat is found on Mainland on the yellow plateaus. They are important to any civilized tribe's diet. There are two parts: the small top part is the ear and the longer bottom part is the stalk.
The ear is used to make bread. It cannot be eaten alone. You must use a quernstone and other things to make the bread. See A Guide To Bread for more info. Bread is an important part of a tribe's diet.
The wheat stalk looks like it's useless, but it can be very useful. Craft four of them to make a wheat bale. Craft two wheat bales and you can get wheat building parts, a wheat bed, or a combat dummy. The wheat bed does not function yet, but you can use the combat dummy to increase your combat level without killing anyone. Repair it when you have killed it. The wheat stalk is also used to reproduce wheat.