That is correct. There are some functional differences in each that should be considered before deciding on which to install.
As Bob stated, a turbocharger is operated by the useless exhaust gas which turns an impeller(a fan) which is connected to the compressor impeller(another fan at the other end of a rotating shaft). This spins at extremely high RPMs ( sometimes as high as 30,000!)and compresses the incoming air-gas charge making it more dense, thereby increasing its energy potential. The absolute best part of this is that this extra horsepower is totally free!(except for the expense of the turbo itself).Its not a perfect solution though: There are two major performance drawbacks to turbocharging. Primary is Turbo-Lag. When the demand for extra power is made by 'sticking your foot in it', the response is not instantaneous.The turbo will not produce any noticeable extra power until the impeller can 'spin-up' to a sufficient speed. This waiting period, sometimes vey annoying, is called 'turbo-lag. Second is the tremendous amount of excess heat that a turbo produces. This extreme heat can cause a lot of pre-ignition(pinging), so the engines compression is generally lowered to compensate, which in turn cause more turbo-lag!
The common solution is to add an 'intercooler' in-line with the turbo. An intercooler is simply an air-to-air heat exchanger, kinda' like a radiator for the air! This will usually bring the super-heated turbo'd air charge down about 100 degrees, reducing the pinging. This also allow more compression, for less turbo lag. The overall size of the turbo, as well as the 'pitch' (angle) of the vanes on the impeller determine how fast a turbo can 'spool-up' to full charge. a 'fast' turbo produces power more quickly, with less overall total power, and a 'large' turbo produces more top end power-eventually.
Because of the extreme heat generated, turbos need careful and timely maintenece. Lubrication is key. For most average drivers, turbos are way too 'finicky' and fragile.
Now a supercharger works with the same principal as a turbo, but instead of using the 'free' exhaust gas to turn the impeller, it is turned by an engine driven belt, as Bob stated earlier. A supercharger operates at RPMs that are much closer to an engines RPM, sometimes exactly the same.Because of this,and the fact that a supercharger is always turning if the engine is on, there is just about no noticeble 'lag'. The extra power is almost instantaneous. The biggest percieved disadvantage to a supercharger is that the extra power is not totally 'free'. There is a rather large amount of engine-power needed to turn the supercharger before it makes any extra power. I know of one set of spec's, only because I own one( ok, my wife owns it, but I fix it!)
On an 89' Thunderbird SuperCoupe ( a supercharged and intercooled 3.8 litre V-6)the engine is rated at 215 horsepower, compared to 145 horses for the same, normally aspirated engine in the standard 'birds.
According to FORD spec's, although the horsepower is 215, it takes over 60 horsepower just to run the supercharger! I believe thisis called 'parasitic horsepower loss'.
It seems that turbocharging has really fallen out of favor with most hot-rodders, and supercharging is gaining more and more poplarity every day. I can see why.One of my nuttier employees has a 94 Mustang GT, came stock with a 5.0 HO, 225 horses. It was chassis dyno'd @ 188 (rear wheel) horsepower, which is about normal for that car. Over the years he has spent about a gajillion of his hard-earned dollars on this car, and a 'Kenne Bell' supercharger is just one of the many mods he has made to the motor. Last year, the car was chassis dyno'd at 550 horspower!Thats at the rear wheels!
Thats not the true power though, because the dyno was not capable of handling ant more than that! That car is freakin' fast!And it is a fully functioning, smooth idling, street legal, daily driven street car! Unbelivable. Whew!
Anyhoo...Don't know if you wanted the whole history of the world, but there you go!
[ December 03, 2002, 09:49 PM: Message edited by: cobravenom71 ]
I think Polynominals were used as well 
