1) section width (which is the width of the tire that is actually contacting the ground.
You may have wanted to say contact patch, which is basically what you described.
Section width is: (From Tire Rack)
A tire's section width (also called 'cross section width') is the measurement of the tire's width from its inner sidewall to its outer sidewall (excluding any protective ribs, decorations or raised letters) at the widest point.