The following are part of Google Ads Exam Certification Answers:
Q) Which bidding type is only available for ads on the Display Network?
A) Target cost-per-acquisition (CPA)
B) Cost-per-view (CPV)
C) Viewable cost-per-thousand impressions (vCPM)
D) Maximize clicks
Correct Answer: C)
Here's the Explanation:
With viewable CPM (vCPM) bidding, you only bid for ad impressions that are measured as "viewable".
A "viewable" ad is when at least 50% of your Display ad is shown on your screen for one or more seconds, or the video ad plays continuously for two or more seconds.
In other words, for vCPM, you bid per 1,000 viewable impressions, but only pay for "viewable" impressions. Effectively, you bid on the value of your ad appearing in a placement's viewable position.
The key benefits are you only pay for the viewable impressions, and your bids are optimized to favor ad slots more likely to be viewable.
More here: bidding on impressions