Explanation: In Salesforce Marketing Cloud, the Subscriber Key is used to identify unique member records. The Subscriber Key is a unique identifier for each subscriber in the database, ensuring that each record is distinct. This key is crucial for tracking subscriber interactions and preferences across different channels and campaigns within Marketing Cloud, maintaining a unified view of the subscriber's engagement and history.

The use of a Subscriber Key enables marketers to maintain a consistent subscriber identity, even if other attributes such as email addresses change, ensuring accurate tracking and personalization.

References: Salesforce Marketing Cloud documentation on subscriber management explains the role and importance of the Subscriber Key in identifying and managing unique subscriber records within the platform.