FPV
The dictionary I'm looking at defines "Vector" as "a line representing a physical quantity that has magnitude, and direction in space as velocity and acceleration.
The aircraft attitude is in relation to the horizon. It could be indicating one degree nose up attitude but descending at a three degree attitude towards the earth. What you would see then is a slight nose up (one degree) attitude on the flight director and at the same time a three degree indication on the FPV. If you could attach a length of string to the nose of the 'plane and extend it to the point of impact on the earth, that would be the plight path vector. Forget about the shape of the 'plane. Think of it as a round ball. So the vector is the path of the ball through the air. It has nothing to do with the attitude of the 'plane.
If you look at the FPV as you fly with a cross wind in flight, you will notice the FPV off to one side, representing the vector of the cross wind. Nothing to do with the direction (heading) of the 'plane.
T