I had no idea too until 2022, when I went to university as a mature student...I have no children, so I am really not "up" on a lot of what's going on in the world with the younger crowds.
Anyway, in one of the modules we had to review a case-study (totally fictitious but based on facts) of a boy whose many interests included ASMR.
ASMR as I now know is listening to everyday noises on a loop, such as fingernails tapping, or someone whispering. You name it, some people can't get enough of it, and I cannot understand it at all. It's like listening to nails down a blackboard - literally in some cases.
I struggle as it is when it comes to hearing certain people speaking, and whispering can cause a red-mist to descend instantly - there are no words to describe how irrationally angry it makes me (it's the same feeling I get when I hear or see the words "cringe" and "judgy" and "chill" being used in place of "cringe-worthy", "judgmental" and "chilled", ditto any sentence written down and ending with a question mark where no question is being asked at all).
Anyway, at uni, luckily for me the tutor was around my age and offered up a disclaimer before showing a Youtube clip that ASMR is really not for everyone, and I am so glad she did, because I could cheerfully have punched a wall. I didn't of course, I simply left the room wanting to scream and slam the door loudly behind me.