You can enter shops and other facilities inside the building and. Similar as in a shopping mall. It is not just an isolated passage through the building, where the walls on your sides resemble the outer walls of the building and you see nothing what is inside the building.
highway=corridor would be possible, but we do not use it much in Slovakia.

sett is rougher than paving_stones. Sett is https://wiki.openstreetmap.org/wiki/File:Granite_Setts.jpg and paving_stones can be https://wiki.openstreetmap.org/wiki/File:Pretty_natural_stone_used_for_paving.jpg . I guess the latter one is what is used inside this building.