Ceramic is often used as an umbrella term to cover all types of
tile from ceramic clay, porcelain and quarry
tile. So not necessarily the actual material.
As per BSEN14411, there are two main classes of
tile. Class A is Extruded ceramics (wet clay moulded and cut to size and fired at just enough temperature to give it the required properties) and Class B is Dry Pressed ceramics (fine clay powder, compressed in a mould and fired at a higher temperature). These are then split down to further bands based on the water absorption rate.
If they are Dry pressed, the will be Class B, then either ia, ib, iia, iib and iiib with 1a being the most impervious (more than likely porcelain) and iiib being the most absorbent (less dense material).
Clear as
mud I know, but may give you an idea