Someone browsing the internet sees Google Adwords display ad for laptop computers on a Google Display Network site, but does not click on it. Two weeks later, the user is interested in buying a laptop computer and decides to visit the site from the ad. The user finds the site by performing a Google search, goes directly to the site, and purchases a laptop. Implementing view-through conversions would be valuable for the advertiser because it could:
- track the IP addresses of the users who saw the ad
- measure the number of conversions that are associated with ad impressions
- track the number of users who saw the ad but did not convert
- measure the number of potential clicks that are associated with ad impressions
Explanation: A view-through conversion happens when a customer sees an image or rich media ad, then later completes a conversion on your site. This is different from a click-through conversion, which happens when a customer had previously clicked on an ad (such as on the Google Search or the Google Display Network) and then completed a conversion on your site.
The last impression will get credit for the view-through conversion. View-through conversions automatically exclude conversions from people who have also clicked your Search or other Display ads.
Read more here: https://support.google.com/adwords/answer/1722023?hl=en