On the Display Network, enhanced cost–per–click (ECPC) automatically:
sets bids to maximize your conversion value while trying to reach an average return on ad send
sets bids to help you get as many conversions as possible
sets bids to help you get the most clicks within your target spend amount
adjusts your manual bid up or down based on each click’s likelihood to result in a conversion
A bid strategy that adjusts your cost-per-click (CPC) to help maximize conversions. ECPC combines manual bidding with a Smart Bidding strategy, like Target CPA or Target ROAS. This strategy raises your manual bids in situations that seem more likely to lead to a sale or other conversion on your website, and lowers your bid for situations that seem less likely to lead to a conversion.
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: //support.google.com/adwords/answer/2464964?hl=en