An effective website design with good search engine optimisation and conversion optimisation is vital to any successful business, but even with these things in place a large number of your visitors will leave your website without ever buying your product, completing your sign-up form/enquiry form, or doing whatever it is that you wanted them to come to your website to do.
Remarketing is a simple and cost-effective way to re-target these people. Once a visitor has been to your website, as they then go on to travel around the web visiting other websites, your adverts will appear on these other websites.