There are as many projections as there are cartographers! A couple of good summaries are at http://www.btinternet.com/~se16/js/mapproj.htm (with a nice applet of projections) and http://erg.usgs.gov/isb/pubs/MapProjections/projections.html with summaries of most common projections. I think you are referring to the Robinson projection (see second link), although it could also be the Mollweide or a number of less-common projections. The USGS describes the Robinson projection as: Uses tabular coordinates rather than mathematical formulas to make the world "look right." Better balance of size and shape of high-latitude lands than in Mercator, Van der Grinten, or Mollweide. Soviet Union, Canada, and Greenland truer to size, but Greenland compressed. Directions true along all parallels and along central meridian. Distances constant along Equator and other parallels, but scales vary. Scale true along 38° N & S, constant along any given parallel, same along N & S parallels same distance from. Equator. Distortion: All points have some. Very low along Equator and within 45° of center. Greatest near the poles. Not conformal, equal area, equidistant, or perspective.