Add New System User Leave both password fields blank for random password generation.

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, Uppler 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.
Write User Info writes user account information to /home/username/.passwd. Includes encrypted password, which can be unencrypted.
PHP Workers is maximum number of PHP processes that this user can have running at one time. Any website(s) installed for this user will be limited by this.