What is the function of an intercooler (charge air cooler) in a turbocharged engine?

1. To cool the engine coolant before it enters the cylinder block.
2. To cool the compressed air coming from the turbocharger compressor to increase its density before entering the cylinder.
3. To cool the exhaust gases to reduce the temperature of the turbine wheel.
4. To warm up the incoming air-fuel mixture during cold engine start cycles.