An internal combustion engine's efficiency and power output are increased by a turbocharger (or turbo), a turbine-driven forced induction device, by forcing more air into the combustion chamber. The compressor's ability to pump more air—and thus more fuel—into the combustion chamber than atmospheric pressure alone accounts for this increase in power output over a normally aspirated engine. A turbocharger's goal is to boost an engine's efficiency by raising the density of the intake gas (often air), which results in more power being produced each engine cycle.
There are several signs you can look out for to tell if your turbocharger has blown: