The Default basemap is

OpenStreetMap PBF Vector Tiles with Terrain/Topo Style

user can change the style to other basemap stylesheets

or user can change to a raster image basemap from different providers * Internet required

Offline area of interest downloads by default osm_vectortiles.mbtiles

you can optionally select contourlines_vectortiles.mbtiles and hillshade_rastertiles.mbtiles and satelliteimagery_rastertiles.mbtiles