[1][2][3] The practitioner jumps into the air and executes a 360 degree turn while keeping his or her body perpendicular to the ground.
[2] As soon as the kicker leaves the ground the kicking leg should be extended as straight and high as possible.
The different variations depend solely on the position of the hips and the direction the toes of the kicking foot are pointing.
The only real difference is that the amount of torque and height needed to execute a 720 is greater than that necessary for a 360.
This happens cause the tricking terms often count the step in part of the move as actual rotation.