When you're working with your subscriber lists, you might want to classify them based on things like characteristics such as age, gender, or location. You might also want to segment them based on activity, such as whether he or she is an active or passive subscriber

What is an active subscriber?

An active subscriber is one whose email address:

• doesn't result in bounced emails (soft or hard);
• hasn't initiated a spam complaint;
• hasn't opted-out.

Essentially, active subscribers are those who are ready to receive emails from your campaigns.