For most boats you have your own air conditioning and a private bathroom. You can book rooms with single, double and sometimes even bunk beds. As a rule, women are sharing with women and men with men, unless you book a man-woman combination yourself.
In the cabin you have some cupboard and/or storage space, but this is limited. If you come on board for the first time, you will see that space is used extremely efficiently, which means that the space in the cabin is not what you are used to at home. Of course there are luxury variants that are very spacious, but that also comes with a price. As a rule you share a room, but for an additional cost of 40 to 60% you can have a room alone. With a bit of luck you’ll get a room only, but don’t expect that when the ship is half full, everyone will get a single cabin. After all, that doesn’t happen in a hotel either.