> Some airports on these maps have runway, and some do not
So to clarify further, in the Plate tab view you can select between
displaying the official FAA "Airport-Diagram" (if published by FAA) or
"Area" (if you've downloaded them) to see OpenStreetMaps unofficial area
maps that show the airport and the nearby street map that's handy for
walking.
Area maps are much more likely to show small airports (for which the FAA
often doesn't supply Airport Diagrams), but are unofficial and thus of
course not recommended for flight. They can be helpful in planning and
in finding your way around on the ground, especially at small or
unlisted airports.