What is the term for a single ad placement available for purchase on a webpage?

The term that refers to a single ad placement available for purchase on a webpage is known as an ad unit. An ad unit represents a designated spot on a webpage where an advertisement can be displayed, and it can take various forms, such as banner ads, display ads, video ads, or even interactive ads. Each ad unit is specifically sized and formatted according to the design of the website and the requirements of the ad campaign.

When advertisers purchase ad units, they are essentially securing the right to display their ads in those predetermined spaces on the site, thus reaching the site's audience. The concept of ad units is crucial for digital advertising because it helps publishers manage their inventory of ad placements, allowing them to sell and track the performance of different ads effectively.

Other terms like ad impression and sponsored post serve different purposes in the advertising ecosystem. An ad impression refers to the number of times an ad is served and viewed, whereas a sponsored post typically refers to content that has been paid for by an advertiser but authored by a publisher, blending advertising with editorial content. Ad slots might seem similar but they represent the availability of ad units rather than identify individual placements. Therefore, the most accurate term for a single ad placement is an ad unit.