Remarketing or retargeting is a type of online paid advertisement which shows ads to such people those who have already visited the website previously. When a web visitor visits a site, a small piece of data gets stored in his or her web browser. This data is known as a cookie. Now, even if that web visitor visits other websites or other online platforms, this cookie will help to show remarketing ads. Advertisers use remarketing ads so that their previous web visitors return to their websites.