The rock and go is leadable syncopation for combining two patterns. Instead of ending the first pattern with an anchor and then starting the second pattern with a walk walk, the rock and go replaces all four beats of the anchor and the walk walk with a two beat connector.
For six-count patterns, the anchor and walk walk would normally be counted 5&6, 1 2. The rock and go changes the count to 5&2. In other words, beat 5 still goes back like the 5 of an anchor. But, instead of letting the follower settle back on &6, the leader turns beat 5 into the back of a coaster step. The follower then attempts to step back on the & like a normal anchor but hits the end of the connection and instead rocks forward on & and steps forward again on what would be beat 6. By stepping forward on 6, the follower should be in the same position that she would be at the end of the walk walk. Thus, we count the rock and go 5&2—we turn the anchor into the position of beat 2.
There are two major effects of the rock and go. First, the rock and go extends patterns. In WCS, a pattern ends with an anchor step. By eliminating the anchor at the end of the first pattern, the rock and go makes the pattern continue. The result is a hybrid pattern rather than two simpler patterns.
Second, the rock and go accelerates the dance by shaving two beats off the pattern. Leaders often use rock and gos to phrase the music; if there is a hit on what would be the third beat of your next pattern, but you want to hit it with a move that accents the fifth beat of the pattern, the rock and go can shave off two beats so you can hit that accent.
However, the rock and go is not a WCS basic. It is not a move that can be lead on a beginner because it changes both the rhythm and the anchor of the dance. In fact, doing rock and gos too much will make the dance look like hustle instead of WCS.