[&The TC& @HTown]

To quickly answer your question, an intercooler "cools" the pressurized or charged air coming from a turbo before it enters the intake manifold. Even an amateur should know that cooler intake temperatures makes for more power. Basically, if you're running a turbo, you need an intercooler. How much power an intercooler will add depends on your application, but one thing is for sure, if you're without one, you will certainly be missing some additional HP