what is EGR,TURBOCHARGER how do they work

I cannot diagram on here, a turbo forces more air into the engine and more fuel is added to make more power basically. it is run by the exhaust from engine and spins about 50,000 rpm's to force the air. the EGR system puts exhaust gas into intake system at different times and rates to reduce NOX emissions so it is re-burning what has already been burnt. the computer controls the rate at which an EGR valve opens.