Kihon kata, also known as Taikyoku sono ichi or Taikyoku Shodan. In many karate schools the applications to the moves are not taught at all. In those that do teach bunkai, the majority teach things that don't make sense. If you have to step out to the left in order to meet an attacker then you are better off not stepping to the left...
However, John Burke sensei has provided us with practical self-defence applications to this simple form, using the moves as throws, joint locks, annd strikes to anatomically vulneable areas. If you would like Kihon to be an effective form of combat, literally back to basics, literally a universal system irrespective of the practitioner's strength and size, then this video, around an hour long, explians it for you.