A colleague partner works for one of the firms that targets your FB with adverts. They are selected by your browsing history. Oddly when I pop onto MN you can guarantee my FB is chokka with adverts for dating sites. This week I cant move for hard wood sideboards.
I always think the most amusing thing about FB is the amount of information freely given; your name, age, school, education levels, employers, what you like for breakfast, your location drops, your childrens names, where they go to school, what clubs they go to, who your relatives and friends are, what interests you have, what groups you join, what papers you read, where you drink, what you eat - governments would have paid trillions for a data gathering tool like this and it's all given freely.
Priceless really for people to be complaining about it.
If you're somebody who worries about crime, you get stories about asylum seekers committing crimes, for example.
That's very simplistic - you would have to (a) follow some news sources (b) perpetually comment on similar stories. I follow several newspapers and I get all their stories - no bot from social media weeds out the eg education ones and spams my timeline because it is my interest. I occasionally get adverts related to education.