What's the difference between Multifamily and Dormitories?

Multifamily Housing is where each unit contains a separate, full kitchen and bathroom. A "full kitchen" has a refrigerator and a stove/oven. A mini fridge with a microwave and hot plate do not constitute a full kitchen.

A dormitory has individual bedrooms (with individual or shared bathrooms), common areas, and either a shared kitchen or no kitchen at all.

So, you could have an apartment building on a college campus, that the university calls a "Dormitory," but because each unit is a full apartment with a full kitchen and bathroom, it is considered "Multifamily Housing" in Portfolio Manager.