crossfit is probably the epitome of conjugate ‘periodisation’. you work on a continuous 3 days on, 1 day off routine with no set pattern to the daily workouts.
for example, day one might be a 5km run. day two might be 120 pull ups and 120 dips (or 30 ‘muscle ups’) as quick as you can. day three might be 10 sets of 3 reps max deadlifts.
there are some set workouts that are all named after girls (not sure why!) which pop up periodically and are usually ‘markers’ for your improvement. these workouts are usually based on time, with the goal of improving your numbers each time you do the workout.
they also make use of olympic lifts on a fairly regular basis.
personally, i think it’s a great system if you are training (and training hard) for general conditioning. however, i don’t think it’s a great system to follow exclusively if you play rugby for example. although the system covers nearly all bases (strength, endurance, power etc) doing a 10km run isn’t necessarily the most conducive to rugby performance!
but crossfit showed be viewed like ANY training system: evaluate it based on YOUR needs. take what’s good, leave what’s bad.
that’s my two pence worth anyway!