When done right, retargeting can be one of the best eCommerce marketing strategies. In short, it is when you track users who have browsed your site and then show them ads while they are surfing the web with the goal of getting them to visit your website again. The logic behind this approach is that users who have already taken an interest in your site are more likely to buy a product later. To ensure it is effective, your retargeting ads should be very specific.