"self contained" vs "room(s)"

What's the difference between "self contained flat or house for rent" and "room(s) for rent"?

• If you have a whole property to rent (ie no current occupants) and you wish to rent it as a whole to a group of sharers (i.e. on a joint and several contract as opposed to individual contracts for each room), you should advertise as a "self contained flat or house for rent"
• If you wish to rent your property by the room, advertise as "room(s) for rent".