Imagine a building of ~60 180sqft apartments broken up into groups of ~6 where each group has a single, shared kitchen. That would be a communal kitchen. There might also be a communal living room. Specifics vary of course.
ok; I didn't figure whether kitchen and anything else is shared, from the site.
It's one of the most common formats for American university students to live in, especially during first or second year, where a study/tv room, sometimes a kitchen, and typically bathrooms are shared amongst multiple rooms of students. Also the rooms often come pre-furnished with basic furunture: bed, desk, and a dresser.