"Yo Yo's" are closure control maneuvers taught in Basic Fighter Maneuvers. The High Yo-Yo is used when you have excess closure, and you roll into lag and go up (controlling closure by transferring kinetic energy into Potential energy), then over-rotate and place lift vector in lead and pull inside the bandit using the additional vertical altitude as turning room to turn "inside" the bandit.
A Low Yo-Yo is used to generate closure...when trapped in lag, you over-rotate and place the lift vector in lead, predicting WHERE the bandit is going and using Gods-G, aka gravity, to help increase your turn radius, maintain your speed, and help you use the vertical turning room to turn "inside" the bandit.
Realize both of these can be countered by an aware bandit who can re-orient his lift vector and deny you the opportunity to take advantage of the vertical.
Obviously roll-rate plays a part in this, but more importantly is the early recognition of the problem and applying the correct maneuver to the situation.
Cheers!
Dobs