When advertising on the Display network it is possible to select ‘all features’ when setting the campaign up, you can then choose whether or not to show your ads in Gmail (Google’s free email service). If this is selected, you can view the metrics discussed in this section.
You can see ads appear under the promotions tab in Gmail (see screenshot below), you will need to click on these ads to expand them, and doing this is what Google charges you for.
Quick Description = The amount of times your ad has been saved
Once an ad has been expanded, it can be saved to your inbox as a message. Google will not charge you for this.
Quick Description = The amount of times your ad has been forwarded to someone else
Google will not charge you for this. The act of forwarding an ad is almost identical to forwarding an email from anyone in your inbox.
Quick Description = The amount of times someone clicks an expanded ad and gets taken to your website
Google will not charge you for this as they only charge you when someone expands an ad. This is however typically the aim of the ad, to get someone to both see it and click on it to go through to your landing page for that ad.