Max - the hinge offset is the distance between the flapping hinge and the rotor mast and is effectively the length of the lever that the blade uses to exert force to move the fuselage. Thus a 2 bladed teetering rotor head has no hinge offset and an articulated rotor head has some hinge offset.
With semi-rigid rotors where some of the mechanical hinges are replaced with composite materials, the exact position of the flapping hinge can be difficult to determine but an 'effective hinge offset' is calculated that equates the actual control power to that which would be achieved with a mecahnical hinge in the same position. For example, the Lynx (with a titanium rotor hub)has an effective hinge offset of 17% which means that the fuselage responds to a cyclic input the same way as it would if a mechanical flapping hinge was located 17% of the distance between the rotor hub and the blade tip.
By control power, I mean how much fuselage response you get to a given cyclic input.