Linux General Question:

The main purpose of NIS is centralizing the authentication
database.

For ex:
Usually when a user try to login to the machine it will
contact the passwd, shadow and group files for user’s
authentication, in case of user requires to access his/her
account across the network we need to update users
information all these files in each machine in the network.
It is bit tricky to organize multiple users’ info in all
the machines in the network.

NIS server will act as central server for user
authentication and all other machines will contact the NIS
server for the user’s authentication info.

Make sure all the machines in your network should be in the
same domain. NIS will work only in single domain.