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.
Boost is the term that people use to describe the air pressure in the inlet manifold. This pressure is essentially the force feeding of air into the engine. An internal combustion engine is an air pump with a little fuel thrown in. In order to burn fuel and make power, air has to be present.