Stands for "Network News Transfer Protocol." NNTP is the protocol used to connect to Usenet servers and transfer newsgroup articles between systems over the Internet. It is similar to the SMTP protocol used for sending email messages, but is designed specifically for newsgroup articles.
NNTP enables both server/server and client/server communication. NNTP servers, for example, can communicate with each other and replicate newsgroups among each other. This is how the Usenet network is created and maintained. In the client-server model, NNTP allows a client system to connect to a Usenet server and provides commands for browsing and viewing articles on the server.