https://howtheyplay.com/individual-sports/How-to-Do-a-Backstep-Guard-Pass-BJJ
Imagine that you're cutting your knee across, three quarters of the way through a very nice knee cut guard pass. Something's not quite right, though. Your partner has baited you, and they now have the underhook! This scenario happens a great deal in BJJ training, and, of course, the BJJ gods have offered up a fantastic solution: the backstep. This technique is not only useful in preventing a back take, but also in helping to secure the guard pass. You might also be familiar with some of the leglock set ups that arise from the same movement.