Ever shop online for a product (a tool or shoes or just about anything) and then see those products again and again? Some call this “being followed around by ads.”
That is remarketing!
While you might find it annoying – it works.
Advertisers are forever confounded by the challenge of knowing whether their spending is working. Remarketing is a way to improve your chances and therefore your ROI on ad spending.
“Half the money I spend on advertising is wasted; the trouble is I don’t know which half.”
Why Remarketing?
After a shopper visits your website you gain a key piece of information. That shopper has shown at least enough interest to stop by. If you further combine information about how long or what that person browsed on your site, you have further clues to their interest level.
A visitor who leaves after a few seconds is certainly not as valuable a prospect as someone who sticks around for several minutes and browses multiple pages. 
With remarketing advertisers can show colorful, visual ads to previous visitors (and more engaged visitors) to keep your brand top-of-mind. Your brand awareness for that shopper goes up.
Furthermore, with per click bidding you get the benefit of showing your ads or logo for free (you only get charged when someone clicks your ad).
That’s why remarketing is frequently in the arsenal of tools used by marketers.
How remarketing works
