All breakfalls are very important since they allow you to land on the ground after throws without causing injury. This breakfall is drilled from the standing position.
From the standing position crouch down and cross your arms over your chest. Be sure to also tuck your chin into your chest.
Now fall onto your back throwing your arms out to the side to break the fall. If an attacker was in front of you, you may want to strike by thrusting your legs to the front.