Protocol

A protocol is the "language" chosen to communicate between two computers in networks.

Popular protocols include:

IP Internet Protocol

TCP Transmission Control

HTTP Hypertext Transfer

FTP File Transfer

Telnet Simple Remote Shell

SSH Secure Shell

UDP Universal Datagram (Raw)

POP3 Post Office (Mailbox)

SMTP Simple Mail Transfer (sendmail)

Jabber open source instant messages

IRC internet relay chat

and others ... (add here)