How does Windows/Microsoft "create" a thumbnail for a video?

Question

Greetings everyone, I'd like to know how Windows and/or SharePoint "picks" the thumbnails for videos stored in the HDD and/or SSD
I am aware this question may sound strange and even nonsensical, therefore I apologise in advance, I'll do my best to try to explain my doubt.
In my experience, not every video features the first frame, or the first frames, as their thumbnail.
The thumbnails are also quite representative of the video itself, either capturing the most important shot of it, or the sequence that I'm focusing and working on, generally for lectures.
This makes me wonder:
How are thumbnails automatically created for videos?

Is there an algorithm that determines an "highlight" in the video, which therefore becomes the thumbnail?
If so, how is this determined? Is it because of some specific "property" of a sequence/shot? (i.e. blur, transitions, colour changes etc...)
Does it search for popular queries related to the video and picks the most popular shot/sequence, in order to make it more recognisable?

Is some sort of AI process implemented in this procedure already?
I have been told about AIs being employed for this purpose, but it might have been a misunderstanding or simply related to some software that integrates it.
Or maybe these very "useful" thumbnails are inscribed in the metadata by the users who uploaded the videos?

I thank you all in advance and, again, apologies for the rather unusual question, but I am rather curious about this process and I unfortunately lack expertise in this field.

Best regards
Francesco

** Moved to the English forum **

Answer 1

Mi scuso se rispondo solo ora, non mi ero accorto di aver creato il thread nella sezione sbagliata...
Tuttavia, non riesco a trovare la sezione inglese dover poterlo creare nuovamente, o meglio: non riesco a capire se stia per riaprire un altro sempre nella sezione italiana o meno...
In ogni caso, la ringrazio per la risposta

Answer 2

Buonasera FraBear,

Essendo questo un forum Italiano, dovresti scrivere in Italiano, per rispetto verso gli altri utenti.

Saluti
Enxo