The Tag-Mapping defines which tags are included in the maps and at which zoom-level they should appear on the map.

Well, easy enough BUT:
If you have an Objekt that includes tags appearing at different zoom-levels ALL tags within this objekt (way/node) appear at the zoom-level of the tag set to the lowest zoom-appear.
EG: You have an area tagged as “industrial” (zoom-appear 10) with an additional tag “caravan_site” (zoom-appear 12) the caravan_site will appear at zoom level 10 if its bound to the object (a poly/closed way in this case).
If the caravan_site is tagged as an extra node it will appear as set in the tag-mapping.

The tag-mapping of the OpenAndroMaps is computed on the fly depending on several parameters, here are the settings for urban areas. Most European maps are based on this setting, with other areas the zoom-appear are different.

tagmapping-min, this is the source for theme composers – according to these zoom-appears the theme should be made to fit all kind of maps, even for Iceland or South-America.