Meta tags and descriptive words from ads and associates them with your IP address, filtering down to your google, facebook, and other social media.. I'd get off google immediately as google tracks EVERYTHING you do.. Since I switched to Duck Duck Go as a search engine, most of those targeted ads have stopped.. But if you click on anything in facebook - even clicking on comments etc, it will track every click and you'll get lambasted with ads for similar junk.. as you know, google and facebook are joined at the hip in this regard..
I would also get off tiktok as fast as possible.. I think tiktok and google are the worst as far as collecting your data and distributing and/or selling it to ad agencies and other entities..
Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..