Vitrified tiles are made by combining 40% clay and 60% silica in a process called vitrification. The process of manufacture makes them extremely hard and non-porous - a great advantage over natural stones like marble which are porous and hence need a good deal of care.
Vitrified tiles are virtually maintenance free and have very good abrasion resistance - which makes them very suitable for use in high traffic areas.
And there is another huge advantage vitrified tiles have over most other floors. The designs on vitrified tiles are printed with soluble salts which are essentially penetrating pigments that penetrate to a depth of 2 to 3 mm below the surface of the tile ... and that means the design is present at depths of up to 25% of the tile's thickness! And the high hardness and abrasion resistance of vitrified tiles essentially means that the design is permanent for all practical purposes. In contrast, some floor polishes exist over the surface of the floor and have little abrasion resistance.
But on the other hand, vitrified tiles are not currently available in a great variety of shades - at least not in as many shades as natural stone tiles are.
Source: Other advantages of vitrified tiles
