A deep clean of a house should be done at minimum once per year although twice a year is even better and you should do some daily cleaning as well.
The meaning of deep cleaning in housekeeping is where you go through the entire house or building and clean it all the way through.
That means that you scrub the floors, scrub the counters, wash the walls, dust the ceilings etc.
You also usually wash sheets, curtains etc.
Basically you clean the entire house or building that you're doing a deep cleaning of.
That includes cleaning the bathtub, shower, toilets etc.
In hotels and motels the deep cleaning refers to taking a hotel or motel room out of service and not rent it out so that the hotel or motel room can be cleaned all the way through.
When you take the hotel or motel room out of the saleable inventory you then go through the room and clean it to more exacting standards than what occurs and is normally performed during the daily cleaning.
Most hotel rooms, motel rooms or guestrooms are deep cleaned between two and four times a year depending on the occupancy level of the hotel or motel.