2D Vector plot: what is being plotted exactly?
 

I am a bit confused with the definition of 'Vector type' in 2-D contour plot. [Flow-3D Ver 10.1]

I am trying to plot the z-velocity contour in the x-y plane with some vectors superimposed on top. For contour variable, I chose 'velocity magnitude'; and for vector type, there are several options as below:

- Plain velocity vector
- Colored by 2D velocity magnitude
- Colored by 3D velocity magnitude
- Colored by 3d component of velocity
- Colored by contour variable

Does anyone know what the vectors actually represent? Is it the velocity vector in x-y plane only? or does it have anything to do with the z-direction?

Thanks a lot!