Whoa, some big misconceptions about superchargers going on here! First, all superchargers are indeed air compressors. That's were the boost comes from. Whether Roots, screw (modified roots; still positive displacement), centrifugal (turbo, Drouin, Pro-charger) or vane (Judson), they all pack more air into a motor than it can inhale at atmospheric pressure, by compressing it into the intake. Also, whenever air is compressed, it heats up, regardless of the type of compressor. (Although some types are more efficient that others.) This is why inter-coolers are used to cool the intake charge.