Bo-Bup is a technique that allow the user to appear behind, next to, above, etc. their opponent instantaneously. There is no noticeable difference between Renewal Taekwondo's and Ssam-su Taekkyeon's.
Trivia
Northern ITF Taekwondo also have a similar technique called Hyperspeed, the difference is that their movement is in straight line and the power of the user's following technique is increased tremendously.