Paleomaps are maps of continents and mountain ranges in the past based on plate reconstructions.
With the discovery of plate tectonics, it became apparent that land masses move relative to one another over time.
It is now possible to construct maps that are probably fairly accurate for continental positions over several hundred million years.
Where rocks are exposed, latitudes can often be determined from the orientation of preserved magnetic fields (see paleomagnetism) but longitudes are based on projections that are increasingly uncertain as one gets further from the present.
The maps are useful since it is usually quite difficult to describe the location and orientation of geographical features using words alone.