GSP stands for Gmail sponsored promotions and is currently one of the newest features out of Google Ads, you have been able to advertise on gmail for a good long while, but Google Ads have introduced new ads specifically for gmail and the above video shows you how.
The first part of it is just the setup of a normal display network campaign – nothing new here. You target gmail by adding a manual placement of:
mail.google.com
Then your keyword is the domain of any site you wish to target. The idea behind this is, if you want to target anyone receiving email from any of your competitors, you type their domain address in and you can target all their customers receiving email via gmail, in the example above I have added competitor.com, but you would choose your competitors website address.
Next you create ads from the ad gallery, this way, when someone hovers over the ad you created, the image expands and they see a much larger ad. You only pay when the person clicks and visits your site. Google have stated some very low costs associated with this new feature, so well worth a test!!!