The listing is incorrect. The room that you see is NOT the room where you will actually stay. You'll stay in a room in an actual B&B called "Alloggio di Luna" (google it), in Piazza Garibaldi, which is a kinda shady area and a bit scary (be careful when you cross the road).
The address that Airbnb gives you is wrong: you'll get one address when you confirm the booking (in a nicer part of town), you'll then receive a different address on the booking confirmation webpage ("Naples, FL, USA", of course it's wrong), but if you ask the host (and thank god I did, otherwise I'd have gone to the wrong place) you'll get the correct address.
The B&B is on the 4th floor, there is a lift but you have to put money in it to make it work (first time I saw this in my life).
The room is… ok? It's clean, but it doesn't feel so. There's a bed, and a couple other beds. Doesn't feel cozy. You can hear the noise from the street below, there are many cars, constant traffic.
The bathroom: I had a private one, in front of my room. Very small, there was no toilet lid, the shower was just ok. Better if you bring your soap.
The wifi didn't work very well.
The host, which is not the person listed here, but her sister, has been lovely. Really great. Very helpful, she told me a lot of places to go to, suggested me a couple of places to eat, explained me a bit of history of the city. Perfect host, from this point of view.
I still wonder why they listed a random room instead of the actual ones…