Someone browsing the Internet sees an AdWords display ad for laptop computers on a Display Network site, but doesn’t click on it. Two weeks later, she’s interested in buying a laptop and decides to visit the site from the ad. She finds the site by doing a Google search, goes directly to it, and buys a laptop. In this scenario, view-through conversions would be valuable for the advertiser because it could:
- measure the number of potential clicks associated with ad impressions
- track the IP addresses of the people who saw the ad
- measure the number of conversions associated with ad impressions
- track the number of people who saw the ad but didn’t convert
A view through conversion is essentially triggered whenever a user is on the Display Network and sees your ad but does not click on it. The user later directly visits your website After finding your site they reach your conversion page and therefore attribute the view through conversion to a particular Display publisher. For a simplified example, if a user views an ad on the display network and does not click but the user later directly visits your website and converts, you would have 1 view-through conversion.
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