The outermost receiver (#1) takes an outside release to lift the cornerback from the flat area. The 9-route here will rarely be thrown to; it is meant to clear the defender. The #2 receiver takes a quick release to the flat and takes his coverage assignment with him. The primary read is #3 who runs the "stick" route. Often times the #3 receiver to one side can force a mismatch with a linebacker or a strong-safety. Versus man coverage, a bursting out-cut at 3-4 yards forces the defender to chase from the inside out. Versus zone coverage, the #3 receiver can sit between two zones and catch the ball for short yardage.
A variant of this combination can stretch the defense vertically by releasing the "flat" route with no depth (quick flat) and running the "stick" combination between 5-8 yards. This forces underneath zone defenders to declare which receiver they will cover based on their depth.
Outside References
1) Breaking Down Woodson versus the 'Tare' route2) How did Stafford, Calvin Johnson beat the Raiders?
3) NFL 101: Introducing the Basic Red-Zone Combinations
4) NFL Preseason 2013: Takeaways and Key Plays from Week 3