A network protocol can be viewed as a common network communication standard, which is used to define a method of exchanging data over a computer network. Network protocols define rules and conventions for communication between different devices, participating in a computer network.
A simple real-world example is human communication. Let us assume that you are a native English speaker and the only language you know is English. If you try to speak to someone over the phone who can speak only Hindi language, the communication will miserably fail. Here for communication between two parties (without the help of a translator), you must need a common language which both parties can understand and speak.
Similar to above example, if computers (or computer like devices) want to communicate each other, they must follow certain set of predefined communication rules. A network protocol is that set of rules that should be followed by different computers or computer-like devices when they participate in network communication.
Almost all protocols used in the Internet are common standards defined by RFC (Request for Comments).
Examples of standard network protocols are TCP (Transmission Control Protocol), UDP (User Datagram Protocol), IP (Internet Protocol), ARP (Address Resolution Protocol), HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), TFTP (Trivial File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), SSH (Secure Shell), Telnet etc.
Devices participating in network communication should know about the common network protocol and communicate according to the way, defined by the network protocol. In other words, standard network protocol software must be running on both devices participating in network communication.
Following example explains it more clearly.
If you are using your browser to browse web pages from a web server (example, www.omnisecu.com), you are using either HTTP (Hypertext Transfer Protocol) or HTTPS (Hypertext Transfer Protocol Secure). The browser you are using must request web pages from the web server using HTTP or HTTPS and the web server must response back to your computer using HTTP or HTTPS.
How HTTP (Hypertext Transfer Protocol) or HTTPS (Hypertext Transfer Protocol Secure) should work were defined initially as a common standard. HTTP was defined initially as RFC (Request for Comments) 2616. HTTPS (HTTP over TLS) was defined initially as RFC (Request for Comments) 2818. Anyone can follow the updated versions these common standards (defined as RFC (Request for Comments) ) and create their own Browser or Web server products.
Now, think about the main benefit in following a common standard. We made a common language so that everyone can speak together without the help of a translator! We achieved interoperability!
Click next link to learn more about RFC (Request for Comments).