Bow Tuning is used to make sure your equipment is setup correctly for your particular style. In particular it is used to make sure the arrows are correctly setup (tuned) for your bow.
It is advisable to seek advice from one the coaches before embarking on bow tuning, below are links to some documents on bow tuning.
Very good guide produced by Easton, Easton Arrow Tuning Guide.
Walk back tuning, produced by Archery Australia.