Let's take this all step by step. Interval training is defined as alternating periods of low and high intensity exercise. The level of high intensity is quite high and the periods of rest are low intensity. This alternating of the two levels of exercise help the heart muscle, provides a cardiac workout while increasing aerobic capacity and allows the person to workout for longer periods of time at higher levels. Interval training is just alternating levels of intensity but may not have the super high levels of intensity as HIIT or Tabata.
High Intensity Interval Training or HIIT is also known as High Intensity Intermittent Exercise (HIIE) or Sprint Interval Training (SIT) is a form of interval training with a burst of maximum intensity training followed by a short lower intensity exercise and repeat again until tired. This type of exercise session usually doesn't last more than 30 minutes.
HIIT routines usually have alternating sections of 30:30 or 60:30 seconds rather than the 20:10 seconds. If you are a beginning you might begin with 60 seconds of low intensity alternating with 30 seconds of high intensity but as you get in better shape, switch to the 30:30 ratio and then 60 seconds high with 30 seconds low. Just know that the longer your session goes, the harder it is to maintain the higher levels of intensity. In addition, it is important to have those periods of rest for HIIT to be effective.
Tabata is a form of HIIT set in a specific pattern. Tabata is composed of eight rounds of super high intensity exercise for 20 sections alternating with a lower intensity exercise for 10 seconds. The whole workout takes less around four minutes from start to finish. In addition, this workout is designed to push your body to the absolute maximum.
Tabata was introduced into the exercise seen in 1996 when Dr. Tabata who tested a high intensity workout done by Japanese speed skaters on college age male athletes after noticing the speed skater's performance improved significantly. The results were quite impressive but they were done in a very specific controlled situation. This lead to the Tabata routine taking off even though not all routines were created the same. The routines with the best results will have high knees, squat jumps, skaters, and sprint intervals. So if you want to follow this path, you need to look for routines that have all of these exercises in them.
So Interval Training is the umbrella over HIIT which is more intense and requires more effort and Tabata when properly done is even more intense, demanding your all. Let me know what you think, I'd love to hear. Have a great day.