I'm not an electronic expert at all, but I'm keen on various electronics and stuff, and I like to watch videos where the different laptops are fixed. And in nearly every repair there is a multimeter used to test different components of the motherboard to see if their resistances/voltages are normal.
I see that he puts one of the multimeter probes to one of the through-holes of the board (which are used to connect different layers of PCB, AFAIK), and the other probe is connected to the component/output he want to test (photo).
But it is unclear for me why do you need to put one of the probes to that hole. How does it work? How is the circuit completed during the measurement?
I've searched for info in the net, but I've only managed to figure out that these holes are called "the ground terminals" and they connect the motherboard to the case of a laptop (guy from these videos calls these holes just "ground"). How does it work?
And also, does it matter to which hole to put one of the multimeter probes (there are several of them on the motherboard)?
*The photo is taken from the youtube video, author: https://www.youtube.com/@notebook31 ; video: https://www.youtube.com/watch?v=KuaqOT-NyKQ&t=752s (at 12:29)