So, if a vacuum is technically a place where air pressure is lower than atmospheric pressure, how does the vacuum system work on our MBs?

I'm trying to read up and get educated on how the system works, but I'm not catching on very quickly. At it's core, it seems the system is a series of tubes with air flowing through them. The tubes connect to different moving parts of the car, forcing them to move one way or another - i.e. the door lock thingy moves into the up (unlock) position because.....there is a tube leading to that thing with air pushing the thing up?

Or, the reason I started reading all this stuff was to investigate a really hard shift from 1st gear to 2nd gear. Many posts point to a possible vacuum leak.

But, I need to understand the basic premises of the system - help?

TIA,

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1984 300D: 275,000 miles (soon to be for sale)

In search of my 1987 300D in anything but white.