The wikipedia article is as good a summary as anything:
http://en.wikipedia.org/wiki/New_Topography
There's a lot more where that came from if you search the web. The exhibition has joined others like The Armory Show or the Salon des Refusés as representing a sea-change in artistic opinion.
The link with Gursky is that he is one of a group of now-famous students who studied under the Bechers at Dusseldorf. Others in the group include Thomas Ruff, Thomas Struth and Candida Höfer.
More background here:
http://www.goethe.de/kue/bku/dos/dfh/enindex.htm http://www.jmcolberg.com/weblog/2007...olaf_he_1.html