Vacuum Leak ?

So I was pulling into a gas station and outside was one of the mechanist and he said that he heard me pull in and thinks that I may have a vacuum leak. I asked him how much he would charge me to take a look at it and he said $50 so I said I would think about it. First off all what the hell is a Vacuum leak? How do I know if I have one or not? And what would I have to do to get it fixed if indeed I have a leak.

Whats your car Ideling at?

1000RPM

Vacuum leaks usually are form a rubber hose that's split. You should be able to hear it under the hood. Wiggle the vacuum hoses while the engine is running and the sould will change. Your car will often idle too fast with a vacuum leak.

If you have an intake on your car than that was what he was hearing, the sucking sound from the intake.

yeah i have a cold air intake. Good thing i have nothing to worry about.