Node editor, Lamp Data "Light Vector"?

The nodes are very confusing and I need help, can someone kindly explain to me what “Light Vector” is? Does it return the lamp objects position in vector or something totally else?

It returns the vector from the lamp to the vertex relative to the camera, I think*

In a slightly easier to understand manner, but less accurate one:
The angle that the light hits the object.

like

vertex.getVectorTo(lamp) ?

is that how a shader works? surface normal vs vector to lamp?

could it be that simple? it just interpolates the averages between the verticies? a normal map just modifies this data?

Bump many questions…

Thanks everyone, I appreciate all the helps and the useful examples, I’m able to figure out how to use light vector now :smiley: