New = Contact has not yet Opted-In: did not click on the opt-in link in the email
Viewed = means the contact viewed a resource, but has not yet opted-in
Opted-in = contact has opted-in to a campaign: receiving the emails from campaign
Opted-in & Viewed = means the contact has viewed a resource, and Opted-in
Unsubscribed = contact clicks the unsubscribe button and will not receive emails from you again.
Bounced = contact did not receive the email, most likely due to bad email address.
Released = the contact has been added as a contact by another user and assigned to a campaign
To know more about different contact statuses, please check this link: Web: What do different Email or Contact statuses mean?