"It is awarded to the horse that earns the most points in three or more events in two categories during the show."
"The team earned a total of 38 points. Un Forgettable won a world championship in senior pleasure driving, reserve championship in senior hunter under saddle, placed fifth in senior hunter hack, sixth in performance halter stallions and 12th in senior working hunter." AQHA World Championship Show: 2013 Farnam Superhorse
There ya go. :)