CrossFit is a strength, conditioning, and overall fitness program consisting mainly of a mix of aerobic exercise, calisthenics (bodyweight exercises), and Olympic weightlifting. CrossFit describes its strength and conditioning program as "constantly varied functional movements executed at high intensity across broad time and modal domains. CrossFit aims to develop fitness in what the company deems to be the 10 components of physical fitness: cardiovascular/respiratory endurance, stamina, strength, flexibility, power, speed, coordination, agility, balance, accuracy. (Definition taken directly from Wikipedia)
The CrossFit Games, created and directed by Dave Castro, have been held every summer since 2007. Athletes at the Games compete in workouts they learn about only hours beforehand, sometimes including surprise elements that are not part of the typical CrossFit regimen. Past examples include a rough-water swim, a softball throw, and a pegboard climb.
The Games are styled as a venue for determining the "Fittest on Earth," where competitors should be "ready for anything”. (From Wikipedia)