If I understand this question correctly, I do believe you are talking about ad targeting. This is how a website will display the ads that you see on the site.
In targeted advertising, they use a sophisticated method to show the ads online that people see. It can make you feel creepy like a person is following you around and watching your every move online. Here is how targeting advertising works.
The displayed advertising is chosen by the actions you do online. What websites you visit, what products you search for, and what items you are researching.
A tracking cookie is entered in your browser that allows the advertiser to know your moves online. They use these tracking cookies to determine what ads they will display for you.
Tracking your browser history gives online advertisers a good idea of what ads they should display for you. This in return will spike your interests to click on these ads to see what they have to offer.
This is how the advertisers gain more clicks and conversion on their ads that they display online.