so facebook says "here embed this code" and now the site/app tells fb everything you do there. fb knows who you are on a creepy-intimate level, so when the soap company buys advertising on fb, they target that advertising at other people who will be likely to make those same purchases
the creepy part is that it works very well. at this point basically every website on the entire internet is sending that data about you back to fb, where they can reassemble it into your entire digital footprint
Speaking of tracking meta-data:
Since my Dad, Sister, Brother-in-law and I all share the same Netflix we really confuse the "recommendations bot" at Netflix.
Unstoppable shitposting engine.