NIS is a Discovery Mechanism.
Sun Microsystems licenses this technology to virtually all other UNIX vendors.
In many environments other Directory Services, which may be considered to be more modern and secure than NIS, such as LDAP, have come to replace it. For example, many LDAP servers run as a non-root user, and SASL-based encryption or TLS/SSL of LDAP traffic is typically natively supported.
The nameserver functionality NIS and probably LDAP can provide maybe better handled by DNS servers when used on large LANs, leaving just site-wide identification information for NIS master and slave systems to serve. However, some functions such as the distribution of netmask information to clients, as well as the maintenance of e-mail aliases, may still be performed by NIS or LDAP.