Answer: Target impression share.
Explanation:
Target impression share is a type of automated bidding strategy that that works by place your ads first, at the top of the page.
It is a Smart Bidding strategy that automatically sets bids with the aim of showing your ads on the absolute top of the page and on the very top of the page.
Target impression share is can either be used as a standard strategy in a single campaign or as a portfolio strategy across or in multiple campaigns.