On all maps you may see some numbers and/or letters. They are described in the each map's legend. Also short description is available as a hint (move mouse pointer over symbol and wait a while - a hint should appear).
Visibility of those symbols can be changed by the "Show Additional Informations" checkbox. Also double-clicking on map should hide/show additional informations only for that map.
In the game every map is connected somehow with other maps. When additional informations are visible you can also "travel" through maps by clicking on proper symbols (numbers) which are made as links.
There are two global maps of Guardia. On both maps are areas which are links to local maps - not all local maps though. But list of all locations is available as the sidemenu. They are divided into three categories (for better navigation) - Cities, Dungeons and Wilderness. I know that this division isn't perfect, but I think that it is better than nothing.
The map "Guardia" shows artists conception of planet Guardia. The picture is taken from internet. I don't know who is owner of this image (probably Sir-Tech - you can show this picture in your browser, there is text about copyrights in the bottom-left corner of the picture) - it was taken probably from site whith "abandonware" games, but you can find many other sites with this image.
The "Game Map (modified)" shows all "visible from above" maps from game joined into one great map. They had to be slightly modified, because original maps assembled together don't match in some points.