From the CF website since they explain it much better than I would...
The CrossFit Games stand alone as the ultimate test of fitness. No test, regardless of its lofty claims, can grant legitimate title to the best without first providing access to all.
The 2015 Reebok CrossFit Games season begins with the online Open. Anyone can sign up to compete in five workouts over five weeks and post their scores online. Last year, the Open reached more than 209,000 athletes from around the world.
You can either perform the Open workout at a participating CrossFit affiliate where you will be judged in person, or you can film your full performance and upload it to YouTube or another video-sharing site. The video will be displayed alongside your score so other CrossFit athletes can be your judge.
You are free to make as many attempts at the Open workout as you please. Your only limit is time. You have four days—96 hours—to complete the week's workout and submit your best score to the Games site. The week's workout is released each Thursday at 5 p.m. PST, and scores are due the following Monday at 5 p.m. PST.
The Open, for me, forces me to do movements that you probably wouldn't attempt normally. So far, this Open has made me attempt and conquer two moves I have never, NEVER, been able to do. Toes-to-bar and Chest-to-bar. While I didn't get any of my awesomely solid nearly 30 Toes-to-bar on video, I did get one of my Chest-to-bar's. Or course I had to make a fancy video for it!
Congrats to my buddy Mirena who was able to get one Chest-to-bar as well!