What is the world's hottest pepper?

According to the Scovile Scale the hottest pepper is Bhut Jolokia. The one you are currently growing

Scovile Scale Visualized

What is a naga jolokia, and where does it stand in comparison to the other "contender" peppers?

Bhut Jolokia or Naga Jologia

According to some sources, they indicate that Bhut and Naga are the same pepper. Naga means Ghost.

MSNBC has a great article covering this world record chili:

The pepper is known by any number of names across India’s northeast. It’s the “poison chili” in some areas, the “king of the chilis” in others. Just to the south of Assam is Nagaland, it’s eaten in nearly every meal. As a result, it is often called the Naga mircha — the “Naga chili.”

The world record holder is currently the Carolina Reaper according to Guinness (as of AUG 2013).

This pepper began its family tree as a crossbreed between a Ghost Chili pepper and a Red Habanero.

The LA Times reports that the hottest Reaper has been clocked at 2.2 Million Scoville units. That's higher than some commercial pepper spray products. They go on to cite a study conducted by Winthrop University (South Carolina, US) that claims the average is closer to 1.5 M.

There is a hotter pepper contending for the throne. "Pepper X" (a codename pending a permanent name) is now supposedly clocking in over 3M but is pending Guinness verification.

What a time to be alive.

According the Scoville Scale the peppers you mention (the Bhut Jolokia chili pepper) are ranked with the hottest of the peppers, albeit in a 'wide range' (855,000–1,463,700 Scoville heat units).

The Scoville explanation on Wikipedia (linked above) does not include "naga jolokia" but does include "Naga Viper" and "Bhut Jolokia". It is likely that "Naga Jolokia" is a hybrid of the two, which may or may not be stable and reproducible. These are all in the that same "hottest of the hot" range and "which is the hottest?" is likely a moving target. Frankly, I would put all of these in the "too hot to matter" category. There is no reason that I am aware of that the average home gardener could not purchase any or all of these varieties and even produce your own hybrids using relatively simple cross pollination techniques.

This answer should not be confused as volunteering to taste or sample anything prepared with any of these peppers.

Let me just clarify why some places will say the Bhut is the hottest and some will say the Viper is the hottest. It's because there are two different notions of "hottest".

One notion is this: If I were to grow some peppers, what variety would get me the hottest peppers on average? The answer to this is the Bhut. They consistently produce peppers over 1,000,000 SHU when grown casually by amateurs.

The other notion is this: What variety is the world record, hottest pepper ever? The answer to this is the Viper. But if you were to grow a Viper casually, you would not get a heat level anywhere near the world's record.

The reason for the discrepancy is not very well known. Most likely, the Viper is just more responsive to the techniques used by expert growers to produce record-breaking peppers. (Controlled light patterns, intentional drought stress, and so on.)

Updated list of hottest pepper of 2016 year is show on this site http://browse-read.com/the-15-hottest-pepper-in-the-world-other/ Carolina Reaper takes 1st place on 2013 year and are there until now. but 2nd and 3rd place are Trinidad Moruga Scorpion and 7 Pod Douglah Pepper :)

The hottest pepper is pepper x even though it does not say that in the book of Guinness(1). The hottest pepper you can grow is the “ghost pepper”. Sadly I don’t know the answer to your first question.

A good crop of red thin Thai peppers. They vary,but when they are strong they are untouchable with a distint aftertaste