I actually looked up Wilks and found this page....
http://www.isu.edu/~andesean/wform.htm
Just google it and you will see the explanations. They basically took the best lifts at the different body weights, then made a best fit curve graph. Using the equation of this curve, they came up with the Wilks formula, which compares your weight to your total lift body weight. By using this compared to the best lifts of all time, you have a somewhat accurate score to compare to others.