In many examples, the group to which the object belongs is immediately distinguished visually, but this is not always the case.
The fritware of the Islamic world does not use clay, so technically falls outside these groups. Historic pottery of all these types is often grouped as either fine wares, relatively expensive and well-made,
and following the aesthetic taste of the culture.
Because unglazed biscuit earthenware is porous, it has limited utility for the storage of liquids or as tableware. However, earthenware has had a continuous history from the Neolithic period to today. It can be made from a wide variety of clays.