To elaborate a little on what T3RM1NVT0R said...
The entry you see is not an account in and of itself. It's used to signal that the system needs to incorporate all login information found in a centrally managed admin system such as NIS, NIS+, and/or LDAP. It incorporates that info by going through/using the nsswitch.conf file. Because you mention 'Yellow Pages' I am left to wonder whether your system is configured for NIS (because--for historical reasons--NIS used 'yellow pages' and/or commands that began with 'yp' for handling NIS information).
Curiously, my personal system's man page for /etc/passwd (man 5 passwd
) does not mention that particular entry format. Though, I did find this page: passwd(4)