As an example I have a burst pipe and I need to call a plumber out to my house. 10 years ago I'd go to the physical phone book and look up a plumber to call. I don't do that anymore now I type "my suburb name + plumber" into my browser.
Where it does not work well is because I searched for the term 'plumber' every site I visit in my browser for the next few days will display ads for plumbing supplies. Or I'll scroll through Facebook on another device (like my phone) and the plumbing ads will follow me there.
The first type of advertising is useful, the second type feels creepy and like the internet is stalking me.