Hi!
What they mean by contour lines is the exact outline of the "end result" - like on a photo or a finished drawing, filled with detail. But gestural lines (or shapes) are meant to describe that in a simplified, expressive manner, just enough information to convey the pose, and general proportions. Where there might be a slight bump on the actual anatomy, if it's not an important part of the pose, it's omitted in the gesture to have less distractions from the bigger statement and get that working first.
"Drawing what you feel" is what I started to understand only after quite a bit of practice. It's an intuition thing that tells me if my drawing is "working" or not. If the gesture works, I can almost "feel" the energy of the pose or shapes, and it helps tremendously to guide my drawings.
Hope it helps, good luck!
