In the hotel (hospitality) industry, a bed night, or bed/night, is a measure of occupancy of one person (assigned to one bed) for one night.
As opposed to standard room/night occupancy, where a room is the unit of measure, a bed/night calculates the number of beds in the entire hotel (a room can have more than one) with the nights each of them are booked.
For example: A hotel has 10 rooms, each with 2 beds. If 5 separate people book 5 rooms for all 30 days in the month of April, this hotel had a room occupancy, or room/night occupancy, of 50% for April. However, there are 20 beds spread out over these 10 rooms. If these same 5 single and separate people booked the 5 rooms for all of April, the bed/night occupancy would be only 25%, because 5 beds were used out of a possible 20 for April.
It can get even more convoluted when you take the nights into consideration. If a hotel with 12 rooms each with 2 beds was booked by 12 separate, single people for 15 each of the 30 days in April, the room occupancy would be 50%, because each room was occupied (100% . . .), but only for 15 of the 30 days (. . . /2 = 50%). However, if you want the bed/night calculation, it would be 25%, because 12 beds were occupied of the 24 available (50% . . .), and for only 15 of the 30 days in April (. . . /2 = 25%). Get it? 🙂