Target CPA bidding can help drive conversions by using your conversion history and:

CPA goals to show the optimal ad when a conversion is more likely
CPC goals to raise your bid when a conversion is more likely
CPA goals to raise your bid when a conversion is more likely
CPC goals to show the optimal ad when a conversion is more likely

Explanation: Target CPA is an AdWords Smart Bidding strategy that sets bids to help get as many conversions as possible at the target cost-per-acquisition (CPA) you set. It uses advanced machine learning to automatically optimize bids and offers auction-time bidding capabilities that tailor bids for each and every auction. Read more here

See all AdWords Fundamentals Questions and Answers here.