As people browse websites on the internet, many websites capture browsing activity and customer preferences in small files, called “cookies.” These cookies allow websites to provide a personalized experience for customers when they return to the website. Cookie matching is a way of correlating the cookies that have been generated by the same person on different websites - this allows one website to purchase targeted ads on another website that the customer visits. This is why you see an ad on Facebook for a product that you just looked at on another website.