http://http://en.wikipedia.org/wiki/Eidetic_memory
Eidetic memory, to use the clinical term, is the ability to recollect an image/sound so vividly that it appears to be real.These people just seem have the ability to organize information with unusual efficiency
Children seem to do it best,because they lack an adult's competing mental clutter, and it fades as we grow older.
To some extent the ability to remember can be learned, although the result isn't photographic memory but simply improved recall.