Answers
What is a conversion action?
The thing you told Google to count as success — and therefore the thing it will buy more of.
The short answer
The thing you told Google to count as success — and therefore the thing it will buy more of.
For a store it should be purchase, marked primary, with revenue attached. Add-to-cart and page views belong as secondary.
Get this wrong and the bidding works perfectly toward the wrong outcome, which is worse than it not working at all.
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