We mentioned the intercooler previously, although we won't go into this in detail, let's get an idea what it's there for. Exhaust gasses are hot, very hot. These pass through the Turbine Housing so introducing high heat into the turbo. The turbo, in most cases, are of a journal bearing design, the lubrication system is fed from the engine's lubrication system, so,again, heat is introduced. As with any rotational parts, friction plays a big part resulting in, yes you guessed it, MORE HEAT!
What we have learnt here is turbos get hot, very hot! in fact, if the car has been used hard and you looked at the turbo (better if in the dark) you can actually see the shaft THROUGH THE CAST HOUSING! The heat is that extreme the metal becomes transparent and you can see the inside of the turbo. Amazing! Well to look at, yes, but, for an engine, it's a really bad idea. Generally, engine's air intake is better the cooler it is; colder air is denser, meaning more air per litre etc, as well as more complex reasons but let's use the above to continue.
Air leaving the turbo is fed through an intercooler. The intercooler (usually an air to air make up) is similar to a radiator. The air passes through small cores over a large area with the outside of the cores having thin fins. The idea is, pushing the air through the largest area possible that, whilst moving, has the outside air passing across the cores surface, hence cooling. The idea behind the fins between the cores is to draw the heat from the cores themselves, dispersing to the atmosphere, as well as to help direct the air passing through the core. This process results in a cooler intake temperature after the intercooler than before.