Audiences allow you to segment your lists based on specific criteria that you choose. The platform allows you to Create Audiences from your current contact lists. To do that, click on the Contacts option from the left sidebar, then select the Audiences tab in the top.
To create your first audience, click on Create Audience. You will be presented with a form window where you can give your Audience a name, choose your source list(s) that will be used to create this Audience (You can leave this option empty to apply the rules on ALL LISTS). Next you can specify your rules, for example, you can group contacts based on their behavior (opened your last campaign), or based on field values (Title field is CMO), or other rules…
This is another screenshot showing more options being used inside the audience settings.
Audiences can be used later on to send specific email campaigns or inside Automation to target a particular group of contacts.