This is the optimization strategy for the account.
Full Budget Utilization: the goal is to fully utilize budget while trying to bring in as many actions (conversion, clicks etc.) as possible.
Optimal Budget Utilization: full budget utilization is not primary goal but rather getting the best CPA or ROAS. The algorithm will not utilize the entire budget, because by doing so the CPA will be harmed dramatically (by allocating budget to campaigns that are not performing well or by raising bids to keywords that are not worthy of this.)
CPA Target: this sets CPA target on account, campaign group or campaign level. The algorithm will take actions regarding budget and bids according to target. Over time CPA will reach designated targets.

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