By contributor Lynn Truong
In addition to Google.com and the Google Search Network, your keyword-targeted ads run on the Google Content Network, too. While search sites will only display your keyword ads if particular keywords are a part of a user's search query, content sites deliver your ads if a page contains content highly relevant to your ads. This is also called contextual advertising. Google analyzes the content, theme, text, and language of the page, and serve ads that closely match. Google will automatically format your ads, and they are always labeled as an advertising/sponsor link. Text ads share the ad unit with up to three other ads on content sites.
You are opted into the content network by default. You can decide to opt out by changing the setting in your account. You can also set a different bid for ads delivered on content sites. To maximize effectiveness, consider creating separate campaigns for search and content networks.
The CPC rate can vary between search and content sites. Google's smart pricing lowers the cost of clicks from ads shown on certain content sites that are shown to have lower conversion rates than ads on search pages. Also, the CTR on the content network has no affect on the ranking of your ad on search results sites. The CTR reported for keyword ads in your account only reflects search network clicks. Because the CPC rate varies between search and content sites, a keyword ad that doesn't meet the minimum CPC bid for search sites may still run on content sites with a lower minimum CPC bid.