The Display Network is one of the largest advertising areas on earth. It is a network of many millions of websites that have agree to allow Google (and Bing) to show text, video and image ads on their sites. You are likely very familiar with these ads and see them every day. But if not, look at the picture below and you'll see red arrows pointing at these ads on a popular website:
The display network is quite different than your regular search ads. There are a couple of main differences.
1. Intent: When people search for something they are directly looking for it. But with display ads the user is surfing around the internet and your ad has to distract them so they click on it.
2. Supply and demand: Even with the most popular products there is a limit to the number of searches for any particular product, service or keyword phrase. If you are a Chinese restaurant in Atlanta there is a limit to how many times people will search for Chinese restaurants in Atlanta. But with the Display network, there really is no limit. The number of sites that have Display ads on them is many, many millions and the internet and Display network just keeps growing. So if only 50 people look for your Chinese Restaurant by doing a search, you can still reach them and many others using the Display network.
A couple of great things about the display network are:
You can make very eye catching image, animation and video ads.
While the amount of searches is limited, the amount of sites that carry display ads is huge and grows daily.
Here's a nice short video explaining the Display Network: