An unsubscribe/update profile link is automatically appended to your newsletters. Contacts can unsubscribe or update their information in your database through this link.

Email addresses from contacts who unsubscribed are removed from your database and moved to a separate "unsubscribed" list. This unsubscribed list is used to make sure that email addresses from contact who unsubscribed are not added back in, and can also be exported.
Screen Shot:  "Unsubscribed" list