Firstly, thank you all VERY much for the responses and help.
Much appreciated.
I was asked this question by my flight instructor and could not give back a proper answer.
I asked about the CFM specifically because we were talking about the airbus as that's the type rating i'm going to do soon, but now realize that it does not matter because any high bypass turbofan engine will basically operate in the same way.
I researched, and alot of answers were a little too detailed and I couldn't understand exactly how the engine worked still.
Thank you all once again, my apologies for being vague.