Targeting (focus of advertising) is management of shows of banners, advertising, implying that the sites where one is to demonstrate advertising are defined based on their subjects orientation or the geographical location of users. Also targeting is possibly based on the time of a day or days of the week.
Targeting allows to customize a show of advertising in such a way as to maximize number of target users to be covered and minimize the show of advertising materials to users that not belong to a group of the potential customers.