How the Google Display Network works
Website and app owners join through Google AdSense and AdMob and are paid for showing ads. Advertisers create display campaigns in Google Ads and choose who should see their ads, by audience, topic, keyword, placement or remarketing list. Google places the ads where those people are browsing.
Display Network vs Search Network
The Search Network shows text ads to people who are searching. The Display Network shows visual ads to people while they read, watch or play, often before they are actively looking. That makes display better suited to awareness and remarketing, while search is usually better for capturing existing demand.