What is GSP?
Known as Gmail Sponsored Search (GSP), Gmail ads are the new advertising solution that allows you to target Gmail users with custom ad formats.
Where do Gmail Ads appear?
GSP ads appear in the Gmail account of targeted users as the top colored message on the "Promotions" tab, and on the right-hand panel or top right corner of the e-mail reading page. Once clicked, it is displayed in the reading panel as a message.