A passenger van combines a road vehicle with a cabin designed around several rows of occupants. Its powertrain turns the wheels, its suspension supports the loaded body, and its brakes slow the combined mass. Inside, seats, restraints, doors, and ventilation make that movement usable for people rather than simply providing an enclosed space.
The systems interact. Adding passengers and bags increases the load the running gear must carry, while changing a seating layout can affect access, luggage space, and attachment requirements. Understanding those connections is more useful than treating seat count as a complete description of the van.