Jock itch (tinea cruris) is a fungus, the same one that causes athlete's foot and scalp ringworm. The groin area is the perfect place for the fungi to grow and cause a fungal infection because it is moist, warm and dark.
The camshaft lift is the resultant net rise of the valve from its seat. The farther the valve rises from its seat the more airflow can be provided, which is generally more beneficial. Greater lift has some limitations.
A lifter glides (or rolls for a roller lifter) on the cam of the camshaft. As the cam lobe rises, the lifter follows this motion and transfers this to the pushrod. This then moves a rocker which in turn pushes the valve open. Camshafts for a 2 valve engine would have one intake and one exhaust cam for each cylinder. The lifters follow each cam, opening and closing all the valves appropriately. Usually, the rocker is set up so that the valve will open further than the cam does.