On the Display Network, enhanced cost-per-click (ECPC) automatically:
- sets bids to help you get as many conversions as possible
- adjusts your manual bid up or down based on each click’s likelihood to result in a conversion
- sets bids to maximize your conversion value while trying to reach an average return on ad spend
- sets bids to help you get the most clicks within your target spend amount
Explanation: Enhanced cost-per-click (ECPC) is a bidding feature that raises your bid for clicks that seem more likely to lead to a sale or conversion on your website. That helps you get more value from your ad budget. If you’re not yet using Manual CPC bidding for this campaign, choose Manual CPC bidding from the drop-down, and check the Enabled Enhanced CPC option.
Read more here: https://support.google.com/adwords/answer/2464964?hl=en