Porcelain and ceramic tile both are part of the larger category of tiles that can generally be called ceramic.
Porcelains are ceramic tiles generally used to cover floors and walls, they are more impervious than ceramic tiles and require much more experience to cut properly.
They have water absorption rate of less than 0.5 percent as defined by American Society for Testing and Materials (ASTM) section C373. They can either be glazed or unglazed.
Porcelain clays are denser and thus less porous than ceramic clays. This makes them harder and more impervious to moisture than ceramic tile.
This tiles are usually about 30% more expensive than ceramic tiles.