The halfshafts are the CV axles, or outer driveshafts. This is a common break item for my car, and I know yours aren't as heavy duty. Wheel hope could induce breakage of either the axle itself, or the joint. You have an open differential stock, so if one blew, you'd just sit there and go nowhere. The input shaft is the one that sprouts from the transmission, and goes into the clutch. If this snapped, your car could rev as much as it wanted, but nothing would even be transferred to the transmission.
