irseg

Basically there are two flat metal plates -- one on the engine (the flywheel) and the other on the transmission (the pressure plate). Sandwiched in between these is clutch disc, which is covered with brake pad-like material. The middle of the disc has a hole in it, which connects to the input shaft of the transmission. When you press the clutch, the two outer plates are forced apart. When you let off the clutch, the two plates move back together, squeezing the pressure plate and forcing it to rotate the input shaft. The "sweet spot" happens when the clutch disc is starting to turn the input shaft, but the friction material is still slipping between the two plates.

As for shifting without the clutch, basically you have to match the speed of the input shaft with that of the gears turning inside. I can do it pretty easily with my T-Bird by giving it just enough gas that it's not accelerating, but the engine isn't slowing the car down either. It's tricky but once you figure out how to do that you can just slide it out of gear and into the next one pretty easily. That only works for upshifts though, I haven't mastered clutchless downshifting. And I can still shift faster using the clutch, basically it's just something cool to show to your friends or if you're having a lazy moment and don't feel like moving your left foot.