If you look at your search term reports and notice that you're getting impressions, clicks and sales on search terms that look like ASINs, you may have wondered what so many customers are doing searching for ASINs on Amazon.
What it actually means is that the impression of the sponsored product ad occurred on a product listing rather than on the search results page. The ASIN is the product listing on which your ad was shown. Here's an example of a sponsored product ad placement on the product listing for an iPhone case:
If you are running an auto campaign, your ads will be shown in these placements automatically and Amazon decides which product listings to target. These ads can be great and will frequently drive sales of your product from competitor or complementary listings. Amazon also recently added product targeting capabilities to manual campaigns allowing you to specify exactly what categories or individual products to go after.
If you notice that some of the ASINs in your search term report are your own products then this means Amazon is showing ads for one of your products on the product listing for another one of your products. These ads can still be valuable because they are still leading a customer to finding the specific product they want and making the sale. However it is best to think about this as branded traffic. Unfortunately if you are running auto campaigns, there is no way of preventing these placements. If you are manually targeting products and you don't want these placements, you can add your brand or individual products to the negative targeting list.