Azkaban is a punishment for users who break the site rules. When you are sent to Azkaban, you will see only one page when you sign in:
You are here until _________ because _________.
The length of time you are in Azkaban differs from one instance to another, but is generally about three days. The staff member who sent you to Azkaban will determine how long you are in for.
During your time in Azkaban, you can not access any features of the site - at all. This does NOT mean that you can create a new account, as that is against the site rules and could result in your expulsion from the site all together, permanently.