Audience targets allow you to display ads to users who have already shown interest in the advertiser's products and services by visiting the website or submitting their contact information. An audience target contains a retargeting list and settings for displaying ads to this audience (the bid and/or priority).
A retargeting list defines the criteria for selecting users. Retargeting lists are used in audience targets and in bid adjustments. To set up a retargeting list, you can use goals and segments configured in Yandex.Metrica, or segments configured in Yandex.Audience.
You can see more details in the documentation.