Refer to figure.
The blades are free to move relative to the hub, the rotor is able to tilt left, right, forward and back. Therefore, we need to define more than one plane of rotation and associated axes.

Tip Path Plane: The tip path plane is the plane traced out by the blade's tips. This plane is also known as the no-flapping plane or rotor disc plane. The tip path plane is parallel to the plane of rotation and perpendicular to the axis of rotation.

Rotor Disc: The rotor disc is traced out by the blade in the tip path plane. The rotor disc is always perpendicular to the rotor thrust.

Plane of Rotation: The plane of rotation, also known as the Hub Plane of Rotation, is parallel to the tip path plane but runs through the centre of the hub. The Hub Plane (fixed reference between the hub and the shaft) is not the same as the hub plane of rotation.

Axis of Rotation: The axis of rotation is the axis about which the rotor rotates, it is perpendicular to the plane of rotation and runs through the centre of the hub.

Blade Pitch Angle: The pitch angle is defined as the angle between the blade chord line and the plane of rotation which acts around the feathering axis.

Main Rotor Shaft: The main rotor shaft axis runs through the main rotor.

NOTE:
You might encounter this question where the options give you "perpendicular to lift" instead of rotor thrust, in this case choose that as the correction and appeal the question since it's not correct.