CrossFit is a form of exercise that focuses on building mass in a leaner way, with an emphasis on weight loss. It is a competitive sport, similar to a decathlon, but with different exercises. CrossFit is different from bodybuilding and weightlifting in that it is more accepting and encouraging. CrossFit gyms don't have the same machines as commercial gyms, and CrossFitters don't usually target a specific muscle group.
Recent studies have shown that CrossFitters suffer no more shoulder injuries than other athletes. The average recreational CrossFitter has a good amount of muscle with a low amount of body fat compared to the average person, while a professional Crossfit athlete has enough muscle to compete with a bodybuilder's physique. CrossFitters focus on speed, high reps, and endurance, while bodybuilders focus on strength and high rep work. Bodybuilders train to create their physique by developing muscle mass and symmetry, while CrossFitters exercise to get fit.
CrossFitters rely on functional movements in their training, such as dumbbell bars, kettlebells, and pull-up bars, and do group workouts in which a large number of people perform the same training as a “class”. If you can get a CrossFitter to do bodybuilding training, they won't be able to perform as well as the bodybuilder. However, every CrossFitter has a bit of bodybuilder in them because when they get down to business, all bodybuilders get an intrinsic joy from lifting a heavy weight.