How does Javascript’s Math.random() works behind the scenes? [on hold]

I've always wondered how on earth does Javascript picks a random number and how can it possibly be random? Don’t computers just take in some input, swirl it around with some math, and then return it?

I'm not asking how to generate a random number with Math.random(), my question is: What happens when you want to generate a ‘random’ number? How does that even work and what’s happening behind the scenes? I understand it's a big topic to discuss but any links will be appreciated!