Contours (Vector Calculus)

OK, I just started Vector Calculus last week, and seriously I'm drawing a big empty hole on some of this shit.

However, I just don't understand contours. Can any one of you anons give me a better explanation for contours? 

contour curves? Think of it as what you would see if you took cross-sections of the curve parallel to the xy-plane. All the points are at the same level there.

By any chance... are you from canada?