a movement where you gain momentum going towards your obstacle, lets say a table, and as you begin the vault you make the initial jump, and depending on which arm you use (only 1 arm) your legs will be in the opposite direction. So, if vaulting over with your left hand/arm, your feet will point to the right, puting your body in a horizontal angle, and vice versa. As your hand touches the obstacle, it restablizes your body back into the position it was before you began the vault, and you continue your momentum in the direction wished.
In short, this vault, done correctly, will have next to no effect on your overall speed and movement as you fly over.
Link is a tutorial video not made by myself.
the speed vault is so amazing it is a rush\