Username is the system username that a website can be installed under. It will be used for SFTP & SSH access. Mixed case usernames are converted to all lower case.
Password must be at least 8 characters with 12 or more being highly recommended.
Passwords under 15 characters must contain characters from at least three of the following four groups:
Lower Case Letters, Upper Case Leters, Numbers, Puncuation/Special Characters.
Passwords 15 or more characters long do not have any complexity requirements.
Jail determines if the user will be "jailed". This is recommended on a Shared Server. Once a user is Jailed it can't be undone by these admins.