TDS vacuum pump

Hey there TDS people, I would like to gladly ask, what is the vacuum pump in our TDS' for? Which systems and components rely on it? How does the pump itself work? Any common symptoms of failing/weak (can it be weak?) vacuum pump? I've read something that it has effect on the turbo too... but I guess it applies only to cars with variable geo. turbos. Does the vacuum pump have any effect on the turbo in our TDS'?