Targeting is the process of focusing an ad on people for whom it is as relevant as possible. Alternatively, the ad could be shown indiscriminately to a broad audience, but very few of them would be interested in it.
For targeting, recipients are narrowed down using various criteria, including demographic characteristics such as age or occupation, geographic data such as location, specific interests and behaviors, devices used, or browsing behavior.
Depending on the channel, various targeting options are available. For example, search engine advertising is heavily based on search terms and search intent, while social networks also utilize extensive signals related to target audiences, interests, and behavior.