You might be wondering if Amazon.com is a Google Search Network Partner or if they are part of the Display Network. The answer is that Amazon.com is BOTH.
Amazon.com is a Google Search Network Partner
Let's walk through an example.
If you went to Amazon.com and searched for "blue shirts"...
You would see Sponsored Links at the bottom of the search results. Take a look at the top ad by ctshirts.com.
If you go to Google and type in "blue shirts", you will see Google search results from ctshirts.com.
Notice that this ad has the same ad text as seen on Amazon.com. I know what you're thinking: "How do you know that's not just the same ad targeted on the Display Network?"
Google doesn't hide the fact that Amazon.com is a search network partner.
The Search Network: Your ads may appear alongside or above search results, as part of a results page as a user navigates through a site's directory, or on other relevant search pages. Our global Search Network includes Google Maps, Google Product Search, and Google Groups along with entities such as Virgin Media and Amazon.com.
So by now, you should realize that when you target Google and Google Search Network Partners, your ad is appearing on sites like Ebay.com, Amazon.com, Ask.com and AOL.com to name a few.
Ads are targeted based on a user's search terms. For example, if you search for "Italian coffee" on a search engine powered by Google, such as AOL.com, you'll see related coffee ads next to the search results.
Amazon.com is ALSO a Display network partner.
To prove it, just use Google's Placement Targeting tool. You can also check out DoubleClick Ad Planner's profile for Amazon.com. According to the placement tool, Amazon.com supports text ads as well as display ads 300x250.
Hopefully this helps clear up some confusion about whether Amazon.com is part of the Search Network or the Display Network. Keep this in mind when you choose Google Search and Search Network Partners within the network settings.