Understanding the difference between a lead and a subscriber shapes how you measure list health and campaign performance. A lead is contact information you’ve gathered, while a subscriber has actively opted in to hear from you. That distinction affects deliverability, engagement rates, and how you should treat each group in your funnel. For the full breakdown of how these two differ and why it matters, read our guide on email leads vs email subscribers. For U.S. compliance context, see the FTC’s CAN-SPAM guide.