Bunkai (分解), literally meaning "analysis" or "disassembly", is a term used in Japanese martial arts referring to the process of analyzing kata and extracting fighting techniques from the movements of a "form" (kata). The extracted fighting techniques are called Oyo.
Bunkai is usually performed with a partner or a group of partners which execute predefined attacks, and the student performing the kata responds with defenses, counterattacks, or other actions, based on a part of the kata. This allows the student in the middle to understand what the movements in kata are meant to accomplish. It also illustrates how to improve the technique by adjusting distances (Maai), timing, rhythm (Ritsudo), and fluidity (Nagare) in combat properly, in order to adapt and adjust any technique depending on the size of an opponent
Now, you may find yourself asking "What about other karate styles ?" or "What about other martial arts?" both of which are valid questions. The thing is, Karate, when studied correctly, when understood properly, is a complete martial art. There are countless martial arts schools that claim to mix Karate with Jujutisu, Krav Maga, Wrestiling, whatever, to make it more effective. This however is totally unnecessary when you consider the movements in your Kata. You realize that if you are studying properly you will be practicing throws, chokes sweeps, knee and elbow strikes, and so on all as part of your karate practice. So don't mix karate with something else, give it a fancy name and think that you are doing anything special. See the videos below from the guys over at Karate Culture.
After watching these videos, you will see what is meant when saying "Karate, when studied properly, is a complete martial art."
Every karate school out there having its own 'style' and fancy name and super grand-master supreme (Or other nonsensical ranks/titles) makes no sense whatsoever. Instead of this nonsense, we should be practicing, developing, and sharing what karate already has to offer. We should be practicing One Karate.