This is the point at which the lift due to angle of attack acts.
Hmm, I'm afraid that is not universally correct.
That would be the Center of Pressure.
The Aerodynamic Center is the Point at which the moment is
constant, independent of AoA, but not necessarily
Null. Yes, generally that is close to the Quarter Chord Line but it depends on the Airfoil (mainly on the Camber) where it is exactly.