Shuffling is a faster movement than stepping. Rather than chasing after an opponent, or running away to retreat, shuffle your feet. With shuffling, the rear foot moves first in this movement, then the lead foot.
Basically, the rear foot ALMOST replaces the lead foot. The rear foot steps up a few inches behind the lead foot, then the lead foot steps forward. To go backwards, simply reverse those instructions. Shuffling looks alot like skipping except there's no hopping and there is no crossing of the legs.