The password is used in login commands such as su and login, or in SSH connection. The default password is alpine.
It is recommended to change the default password after jailbreak, especially you have OpenSSH installed.
Be sure to remember the changed password(s) because there is no way to restore it except restoring your device.
Support iOS 3.0 and above (including the latest 6.1). iPhone, iPod touch and iPad are all supported.