Housing is defined as the part of the settlement, the housing facilities, where the people have their personal space, be they apartments or the equivalent of actual houses. It is different from lodging facilities where the occupants are expected to be transient.
On Mars, housing needs to provide a breathable atmosphere, protection from radiation and a comfortable environment. It may have external windows, but these need to be designed in a way that prevents excessive radiation exposure. Artificial lighting is likely to be standard.
Housing may come from Earth in the form of modules that can be assembled together with other elements to create a settlement, or built on site with in-situ resources.
Minimum living space for housing depends partly on cultural elements, but varies from a minimum of about 10 m2 per person to a comfortable 40m2 per person and 60m2 per person in the US and Canada.