The digital aviation and obstacle data that we make available at no charge on our website enables SkyView to draw airports, airspaces, and obstacles on the map. It's also the data that allows SkyView to be "aware" of all of these entities so that you can flight plan and pull up detailed info on all of the above entities. Other free databases that you install from our website include regional terrain data (draws the topographical background on the map, enables synthetic vision, and gives SkyView awareness of ground elevation to determine things like AGL) and basemap (draws major roads and rivers over the terrain background).
In contrast, the map subscription from Seattle Avionics and other providers (primarily outside the US) are digitized versions of the paper VFR and IFR charts (sectional, IFR Low, and IFR High) . They are georeferenced so that when you turn them on, they appear over SkyView's own map aligned in the right places. While the digital data has fairly comprehensive information (and often more than a sectional when it comes to airport remarks, additional airport frequencies, etc), the charts often have information that doesn't neatly package into the databases. Examples of this are special procedure VFR routings through class B airspace, or notes about nonstandard flight rules areas or special features of airspaces. The Seattle Avionics subscription also includes georeferenced FAA and SA-produced airport diagrams for ~5000 airports.