Google Sites is a free product that makes it easy to create websites. It's pretty basic, and it's designed primarily to be a group site or intranet, where you can share documents, calendars, etc.
Now, Google is allowing AdSense to be displayed on these Sites. Publishers have the option to place AdSense in the sidebar as well as the main content of each page.
Check out this video for more details:
Optimising Digital Marketing Campaigns with Search, Social and Analytics
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