Google Adwords, advertising networks & Format
About Google's advertising networks
With AdWords, your ads can show on one or both of Google's advertising networks: the Google Search Network and the Google Display Network. The campaign type you choose determines which of these networks your ads will appear on.
Search Network
The Search Network includes Google Search, other Google sites such as Maps and Shopping and hundreds of non-Google search partner websites (like AOL) that show AdWords ads matched to search results.
The Search Network can help advertisers to do the following:
Show their text ads next to Google search results
Reach customers actively searching for their specific product or service

Display Network
The Display Network includes a collection of Google websites (like Google Finance, Gmail, Blogger and YouTube), partner sites and mobile sites and apps that show AdWords ads matched to the content on a given page.
The Display Network can help advertisers to do the following:
Use appealing ad formats to reach a wide range of customers with broad interests
Build brand awareness and customer loyalty
Increase engagement with customers
Choose more specifically where their ads can appear, and to what type of audience
The Display Network is a collection of websites – including specific Google websites such as Google Finance, Gmail, Blogger and YouTube – that show AdWords ads.
Here's a list of ad formats that you can use on the Display Network:
Text ads
Image ads
Rich media ads
Video ads