The red areas of the map have the highest surface salinity, and the purple areas the lowest.
By tracking changes in the salinity of the oceans, scientists will be better able to understand ocean currents and the movement of fresh water. For instance, the satellite captured images of the effects of tropical storm Lee as it hit Louisiana, causing the Mississippi River to discharge much more than it usually does, which led to a corresponding area of lowered salinity, pictured below.
The salinity of the area was only temporarily lowered, as can be seen in the middle image above. Read more about the data from this time period here: http://photojournal.jpl.nasa.gov/catalog/pia15185
You can see the current location of the satellite here: http://aquarius.gsfc.nasa.gov/cgi/whereis_aquarius
To read more about the first map, go here: http://www.nasa.gov/mission_pages/aquarius/multimedia/gallery/pia14786.html
For more information about the Aquarius project, visit http://aquarius.nasa.gov/