Sponsored Search Auto Campaigns: These are the first types of campaigns that most sellers start with. All you have to do is specify the products that you want to advertise and your budget and Amazon does the rest.
Amazon will then show your products for keywords that are a “close match” and even a “loose match” on the Search Results page. Amazon will also show your products on related product pages for “Substitutes” and “Complements”, however until now your budget and bid was the same for all of these types of advertising.
Update: Here is what is new! You can now bid separately for Search and Related Products. This is huge and follows the new release of product targeting for Manual Campaigns.
Here is the catch! This is ONLY for NEW Campaigns, it does not show up on older campaigns. So if you want to use this feature you need to create new campaigns and risk loosing your built up quality. Standard practice would dictate that you do this slowly. However, if you have significantly worse performance on Search or Sponsored Products (look at your Search Report) then you may want to do this switch more quickly.