Executive Residence

The Executive Residence is the central building of the White House complex located between the East Wing and West Wing. It is the most recognizable part of the complex, being the actual "house" part of the White House. This central building, first constructed from 1792 to 1800, is home to the President of the United States and the First Family. The Executive Residence primarily occupies four floors: the Ground Floor, the State Floor, the Second Floor, and the Third Floor. A two-story sub-basement with mezzanine, created during the 1948–to-1952 Truman reconstruction, is used for HVAC and mechanical systems, storage, and service areas.
This level was added during the 1948-to-1952 renovation, and contains the air conditioning and water softening equipment. The sub-basement and mezzanine also contain storage areas, the heating system, elevator machinery rooms, an incinerator, a medical clinic, a dentist's office, the electrical control system, a laundry room, and flatware and dishware storage.

Wikipedia