These are special traits used by Addressable Audiences. Active Audience and Data Source Synced Traits are located in Audience Data > Traits > Audience Traits.
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An Active Audience trait contains all of the devices under management in your Audience Manager account. You can use an Active Audience Trait like other traits when you build or edit segments. Also, Addressable Audiences requires this trait to generate overlap data. All accounts have an Active Audience trait by default. This trait cannot be deleted.
Data Source Synced Traits appear in the Audience Traits folder when you create or edit a datasource and apply either of these settings:
Data Source Synced Traits track all of the users associated with a data source. You can use a Data Source Synched Trait like other traits when you build or edit segments. When you create a Data Source Synced Trait, the trait name matches the name used by your data source. Edit the data source to change the trait name. These traits cannot be deleted.
Data Source Synced Traits are useful for troubleshooting. Click a trait name to check the metrics on the trait summary page. If your selected trait returns data, that indicates the ID synchronization process is set up properly and pushing data to Audience Manager.