That link was interesting - I didn't know what Tabata was, other than a word I keep seeing. One of the videos on the site has a 4x4 session but from your text and the text on the site it looks like the actual session can be just 4 minutes. I imagine you don't need to do cardio if you're working all-out like this!
Correct, the whole workout is 4:00 long. No need for cardio, it already is.
Here's a squat example. The Asian woman in the white sweater is doing them with full extension at the top and bottom. She's Annie Sakamoto, a Crossfit legend. 20s of squats/10s of rest in the bottom position, done 8 times. Then you're done, literally and figuratively.
Your 'score' is the lowest amount of reps in a 20s period. The idea is to keep a rep number and maintain it. You don't want to start out with 20 squats at the 1st round because you may end up with 5 squats on the 8th round, making your score 5. Anyone, of any ability can do it, you scale it to your existing ability. If you can't squat all the way, just go as low as possible, keeping good form w/ knees over toes and back in proper alignment. The hardest part? Walking afterwards...http://www.youtube.com/watch?v=ku-eOGXScOQ