Class B Motorhomes are like mini-Class-A Motorhomes.  Added roof extensions offer greater interior clearance and comfort over the stock van. Manufacturers have been very creative in space utilization in many of these units.  

Class B Motorhomes are fully self-contained, with a refrigerator, sink, hot water, air conditioning and heater and comfortable sleeping facilities.  Many have showers and toilet.  Although smaller in capacity, they even have holding tanks for your fresh water, LP gas and sewage capacities.