To make it on the world tour, you need to be able to surf at the highest level both frontside and backside. So what does that mean? Well, you're either a goofy-foot or a regular-foot. It's a bit like being born left or right handed, in the sense that you don't pick.
Waves either break left to right, or right to left, and that means that at any given break, some surfers will have their back to the wave -- on their backside -- while others will be facing the wave -- their frontside.
Backside surfing, especially in heavy waves, is considered far more difficult than surfing on your frontside, and that's why this is such a critical skill if you want to make it on the Championship Tour. Many excellent surfers have found that once they get to the CT, they aren't as comfortable as they need to be with their back to the wave.