The Subscriber State tells you the status of your Subscriber, whether they are Subscribed, Unsubscribed or Cleaned.
Subscriber States Defined
Subscribed: These are phone numbers that are subscribed to your list, which means they're receiving your messages.
Unsubscribed: These are phone numbers that have unsubscribed from your list, which means they're no longer receiving your messages.
Cleaned: These are phone numbers that we're unable to send messages to, so we've stopped massaging them. The reasons why we can't send a phone number a message varies greatly, but a few examples would be: Their cell phone carrier turned their service off, they switched carriers, there was a short code block recently placed on that particular number.