The number of faces refers to how many different patterns are random printed on the tiles.
Tile faces can vary from just 1 on basic tiles model getting 3 to 4 faces in premium ranges. A tile with 3+ faces will look extremely realistic when laid, as it is less likely to see two tiles that look the different design. A tile with fewer faces will repeat the same pattern over and over and when a pattern is noticeable it will look more artificial. A high-quality tile will have a degree of variation between the tile faces to make it look more authentic. The below photo on the right shows a tile with just 3 faces and a repeat pattern, in comparison to a tile with 69 faces (left) where the marble looks more realistic.