Google Display Ads are different from Google search ads, Google display ads are ads shown to website visitors across more than 2 million websites, videos, and apps. Display Ads will be shown on any website that is part of the Google Display Network.
Based on the website viewers online activity, you can target Display Ads to users that have previously visited your website, or a similar website to yours. You have probably been on to a specific website and after that, you see their ad pop up on other websites you are on. The Ad you are seeing here is a Display Ad, it has been targeted to you through a method called remarketing.
Google will know the interests of all their searchers, by collecting data about their recent search history has been. This means you can choose your audience based on these insights. When the user is browsing a website that allows Google Ads, your ad can pop up. Regardless of the topic of the current website they are looking at is, your ad can be shown to the user. We call this an engagement audience.
Another method we mentioned above was remarketing. Using cookies, Google knows who has been to your website. You can then place an ad in front of any user that has visited your website. Timeframes can be anytime from the last 7 days, to all time.