A name service or naming service provides a centralized location for information used by users and systems to communicate with each other across the network. The name service not only stores the information but also provides mechanisms to manage and access that information.
This information is referred to as a namespace and typically includes the following:
Hostnames and their IP addresses
User accounts and their passwords
Without a centralized name service, each system would have to maintain its own copy of the information. For example, by default the Solaris 9 system uses the /etc/hosts file to resolve hostnames to IP addresses. This is fine for a small number of systems, but for a large number of systems, ...