I've been using most Windows 10 versions. At home and at work. Currently this Windows is 1903. I live in Europe. No really, I want to understand how ads are sh

I've been using most Windows 10 versions. At home and at work. Currently this Windows is 1903. I live in Europe. No really, I want to understand how ads are shown on Windows on some people since I haven't seen them myself and the dozens of people I see using Windows 10 don't see them either. Why do you think it's prevalent but I don't see them? Are the ads in some part of Windows that I rarely use? How do they show up? Maybe I actually see them but don't think they are ads.