The vitrified tile is also porcelain tile. Rather, most vitrified tiles are porcelain tiles in terms of its composition and the manufacturing process. 

However, the term vitrified refers to an additional step in the manufacturing process that makes the porcelain tiles even harder and stronger.

During the production stage, the porcelain tiles are vitrified by further refining the minerals used and firing the tiles at even higher temperature.

However, for all particle purposes the porcelain tile would have almost the same resemblance with vitrified tiles.

The term porcelain tile is more common in the US and European markets. Whereas, the term vitrified is more commonly used in the Asian markets especially in the Indian tile market.