Rentometer classification on building type

[Ryan Moore]

I'm playing around on rentometer and their search options are 'house/duplex' or 'condo/apartment'.  I don't really know how to classify units I'm researching that are part of a 3-plex, 4-plex, etc.  I know they are not condos, but do you think the system is calling them apartments?  If so, is calling a tri or quad an apartment a standard thing?