What role does the Subscriber Key play in a sendable data extension?

The Subscriber Key is fundamental in a sendable data extension as it serves as a unique identifier for each subscriber. This unique key distinguishes each individual within the data extension, ensuring that subscriber records are not duplicated and that their information is accurately tracked. The Subscriber Key can be mapped to a specific field within the data extension, enabling personalization and targeted segmentation for email campaigns. By using a unique identifier, marketers can effectively manage subscriber records and maintain data integrity, which is essential for delivering relevant and compliant messaging to recipients.