What exactly is Tabata ? Is it just a form of HIIT ?
What makes Tabata effective in fat burning or providing thermogenic effects ?
It originated from a study performed by Dr. Izumi Tabata in which he discovered that the short bursts of high intensity were far more effective than slower paced, even rythmed exercise.
As for myself I have only implemented it with sprinting after reading more about it in this article from Mark Sisson, but I can say that it certainly does seem to be very effective and exhausting!
This is the single most exhausting training that you could take and yet it lasts so little. Regardless of the shape you are in, it's really hard. If you are in great shape, your sprint will be faster. If in mediocre shape, your sprint will be slower. But in general, if you push yourself, both types will be barely breathing at the end. :)
I don't recommend trying it if you are not in at least a reasonably good shape. There's an excellent Guerrilla Cardio iPhone app for it as well.
The base assumption is that after punishing yourself for those 4 minutes, you body is overloaded heavily and it will take hours to get back to normal rhythm. And for those hours, your blood will run faster through your body and thus chip away the accumulated fat. Hence it's recommended to do this on the off-days, when you are not practicing other stuff (gym, running etc).
Here's a link to the Library of Medicine article discussing the effectiveness. Yes, it's a form of HIIT, the basic idea is 8 - 20 second intervals followed by 10 seconds of rest. Is it effective? the studies performed have shown it to be and I can tell you from first hand experience that it's the most effective program I've used to build endurance and loss weight (real weight, not just temp water weight). Like any other program, you get out of it what you put into it. You need to push the intensity of each exercise as much as you can and limit the rest periods between the exercises. You can apply the Tabata protocol to any body weight or light weight (including kettlebell) routines you have.
Here's the link to the Ross Training article again: http://www.rosstraining.com/articles/tabataintervals.html - worth reading a few times.
Here's a link to an interval timer I use: http://gymboss.com/ (you can also download iPhone timers).
Apply it to heavy bag training, running, kettlebells and you will be very happy with the results.