Absolute Velocity is the velocity of air in relation to the rotating blade.
Absolute velocity = Blade's rotational speed + Air speed flowing along the axis of the engine.
Absolute velocity determines the blade's angle of attack.
Tips of the compressor blades have a higher tangential velocity than the roots.
Thus angle of attack on the blade will differ from root to tip.
To maintain an optimum angle over its entire length the blade is twisted (root has a higher angle than the tip)
Stagger Angle: It is the amount of twist.