Ad Rotation is how Google can deliver your ads on both the Search Network and Display Network. It allows for the best ad to be shown at any given time, so the user sees the right ad and they aren't competing with each other.
Why should you optimise Ad Rotation?
When you have multiple ads in an ad group, only one of them can be shown at a time. As a result, it becomes important to optimise how your ads rotate in relation to each other, and so that the right ads are being served at the right time.
By optimising ad rotation, Google uses signals of keywords, search terms, device, location and more to prioritise ads that will perform better depending on the customer. As more data is collected, ads will serve that are statistically likely to perform better, powered by Google's machine learning.
This may cause an imbalance in the clicks and impressions of certain ads, as the best serving ads will be shown. However, this should make the ad campaign more efficient as the most appropriate ads are being used, but could result in information not being shown.
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