A wood-fired oven can be built of brick or clay.
A fire is burned in the oven for one to four hours (depending on the mass), the coals are pushed to the back for pizza baking or raked out for bread baking. The oven floor is brushed or swabbed with a damp mop and then the food is cooked using the heat stored in the oven mass. Wood-fired bake ovens are used to bake crusty bread, crisp pizza and just about anything else including the Christmas turkey.
The oven can have a barrel/vault shape or it can be round. The inner workings of the oven can be of modern firebrick material or simply made of clay like the early settlers used. Plan your oven location if you can so it can be used in any weather.