DoubleClick Search overview
A remarketing target is created when you apply an AdWords remarketing list to an AdWords manual campaign, Shopping campaign, or ad group.
An ad group remarketing target is used to reach customers who have previously visited your site by optionally specifying bid adjustment or displaying different ads.
An AdWords remarketing list can be applied to an AdWords campaign or ad group for negative remarketing as well. That is, to exclude the members of list from receiving additional ads.
A bid strategy can manage or recommend bids for a remarketing target.