Safety falling, or nak bup, is the art of learning to break a fall and land in a way that will minimize injury. This skill is taught in taekwondo and is also useful in every day life. Taekwondo teaches training in ways to break a fall falling forward, back, to the left, and to the right.
Falling Forward: To break a fall forward it is important to resist your instinct to land in your hands with your arms outstretched. Landing in such a way as that can make it easy to break your wrists. When you are falling forward, land on your forearms therefore keeping your face from smashing into the floor while still protecting your wrists.
Falling backwards: The technique for breaking a fall backwards is very simple. When you land stretch out your arms so they are perpendicular to your body in a T. This helps stabilize and protect your body. The only other thing is to make sure to land with your head still elevated off of the floor. Slamming the back of your head into the floor is probably not the best idea.
Falling left or right: Breaking side falls is the most complicated technique of safety falling. The reason it is so difficult is the same as when you are falling forward. The tendency is to try and break your fall with your palm but this can cause you to break your wrist. Therefore, the technique is to tuck whatever arm is closest to the floor into your side so it is parallel with your body. This way when you fall, the weight of your fall is distributed along the entire side of your body. Same as with falling backwards, make sure to fall without letting your head touch the ground.
Safety falling is probably the most practical part of taekwondo training because you may never get in a fight but odds are you will fall down at some point.