Remarketing refers to the practice of serving ads to people who have already interacted with a company's website or advertising. This is done by placing a tracking cookie on a user's device, which is used to collect information about the user's browsing behavior. Based on this information, companies can target users with specific ads that are relevant to their interests. For example, if a user has visited a clothing retailer's website and viewed a particular dress, the retailer may choose to serve an ad for that dress to the user on other websites they visit. See more