Google Display Network is a new umbrella name for all Google ad properties, where you can buy ads through Google: YouTube, Google properties such as Google Finance, Gmail, Google Maps, Blogger. Over one million Web, video, gaming, and mobile display partners.
"Our display partners include all of our AdSense and DoubleClick Ad Exchange partner sites that allow text and/or display ads. GDN offers all ad formats - text, image, rich media, and video ads - enabling you to unleash your creativity and engage potential customers across the Web.
You can run ads on GDN the same way you always have. Either place bids through AdWords or make reservations on YouTube and Google Finance with help of a Google account team.
In coming weeks, you'll see a change in AdWords interface reflecting this new term, and you'll see GDN where you might have seen Google Content Network mentioned. We've also launched a new website showcasing the sites and benefits available to you on GDN," revealed Google.