Cron it you want a technical simple(-ish) description :the angle of attack is the angle between the blade chord line and the relative air flow. If there is no induced flow, then the relative air flow is coincident with the plane of rotation. Introduce induced flow, and this results in the RAF being a resultant of the two airflows over the blade(from the plane of rotation and the induced flow). The induced flow causes the RAF to move away from the POR vector and towards the Chord Line, thus reducing the angle of attack.
Hope that helps???