Site administrators can go to a user's account page > Permissions & Status to manage the status of the account. There are four possible statuses:
Unknown - This is the default status for newly-created accounts. Once the new user clicks the verification link that's emailed to them, their account status will automatically change to 'verified.'
Spammer - The user will not be able to log in; they will see a message which says "Your account has been temporarily blocked due to suspicious activity. Contact [email protected] to resolve this matter." A user with multiple accounts or with a typo in their email address (such as @gamil.com instead of @gmail.com) may be designated as a spammer.
Verified - The account is in good standing and the user can log in. This is the most common account status.
Banned - The user will not be able to log in; they will see a message which says "Your account has been blocked by your administrator. Contact [email protected] to resolve this matter." The only way an account can be in this status is if a site administrator manually changes the account 'banned.'