A rooming house, also called a “multi-tenant house“, is a “dwelling with multiple rooms rented out individually”, in which the tenants share bathroom and kitchen facilities.
Also called a boarding house the concept is left over from earlier times. Before the great migration from countryside to city more people lived rurally. Young people would come to the city to find work and live in an extra room being rented out privately or in a rooming house. This is also where the term “room and board” came from. It was typical to pay a weekly fee and your meals were provided.
Many cities have gotten rid of these types of rentals. They still exist in some cities as does a whole demographic of people that stay in them. Most people are probably unaware of their existence.
Many of these places have evolved away from rural transients looking for work to something more like an affordable option for temporary or even permanent lodging.