I hafta agree with McDave. I own the DVD that he is referring to, and it is a very easy to understand, down to earth explanation of how the arrow flexes when shot, and how that effects accuracy. It's a difficult task, for most people, to explain this very technical and somewhat complicated phenomenon in a short, typed post. It's much easier to explain with visual demonstration.
BTW, the 3rd volume of the same series is also a wonderful starting point for a new archer, as a more in-depth exploration of the mechanics of the SHOOTING process. Those are the only 2 volumes of the 4 in the series that I own, (and therefore the only ones that I can fairly comment on), but I highly recommend them for helping a person wrap their mind around the concepts involved in shooting a "simple" stick & string.
Welcome to the brotherhood and addiction that is traditional archery!