[math-fun] Chess ratings probability distribution function

I found this (somewhat old) picture of the distribution of chess ratings: http://zwim.free.fr/ics/rating_distribution.gif It isn't exactly Gaussian, but it seems to have Gaussian qualities. 1. Has anyone done research on the distribution of chess ratings? 2. What is the _interpretation_ of chess ratings? I.e., if A has chess rating Ar and B has chess rating Br, what is the probability that A beats B?