Mozilla created a site called Track This that demonstrates how advertisers track the sites you visit and the searches you make in order to show you related ads when browsing the web. Mozilla created the site where you can pick from four personas that represent different interests. When you select a persona, the Track This will open 100 sites related to the persona you selected so that advertisers are trained into thinking that is the subject matter you are interested in. When selecting this option, the page will open sites such as Supreme, StockX, Grailed, Flight Club, Kith, Goat and many more.
Source: https://www.bleepingcomputer.com/news/technology/track-this-demonstrates-how-advertisers-track-you-on-the-web/