What does the concept of "viewability" in digital advertising refer to?

The concept of "viewability" in digital advertising specifically refers to whether an ad is actually seen by users. This metric assesses whether the ad appears in the user’s visible window on the screen for a specified amount of time, which helps advertisers ensure that their ads are not just served but are likely to be noticed by the audience.

Understanding viewability is crucial for advertisers because an ad that isn’t seen cannot deliver its intended messaging or create engagement, regardless of how many times it is displayed. This focus on actual exposure rather than mere impressions helps in evaluating the effectiveness of ad placements and optimizing campaigns for better performance.

The other concepts mentioned in the options do not align directly with the definition of viewability—clicks and display counts assess different metrics of ad performance, and cost-effectiveness pertains to the financial aspect of running ad campaigns rather than how visible the ad is to users.