Consider this. You visit a supermarket/department store. Have a look at some shoes, maybe even try some on. From the footwear section you go onto the dairy aisle and you compare cheese to decide what will work best for your dinner party that night. Without purchasing anything you go on with the rest of the day. Now imagine having somebody follow you around on that same day reminding you of those red shoes you tried on, or that block of cheese that really was good value for money. What are the chances that because of these reminders you go back to that shop and purchase those goods or similar? The key thing is you went back to that same shop. That therein is the principle of Google Remarketing.
The tool can be applied in several ways. Initially you may decide to target everyone who visits your homepage, however, the costs incurred for this will be considerably high. To narrow the focus and increase the relevance of advertising, remarketing lists are recommended. These can be numerous and as varied as you require with the option of adding other targeting methods such as demographics.
Ads that are used for remarketing purposes within the Google Display Network can take several forms including text, images, video or rich media.
Aside from the obvious advantage of remarketing, that your customers are encouraged to buy from you; there are other benefits, namely brand exposure. Furthermore remarketing allows you to maintain a connection to visitors of your site, even after they may have forgotten about you.
Despite best efforts, it is worth noting that users do have the option of opting out of seeing remarketing ads and can do so easily by making changes to their browser settings.