When you connect computers together, you get a “network” which allows computers to “talk” to each other. This communication was originally part of the “operating system” of a computer. The Internet originally arose as a bunch of UNIX-based (UNIX is an operating system) computers linked together, so a lot of the terms on the Internet have their origins in the UNIX world. This means a lot of weird cryptic terms or acronyms are used (words made up from initial letters of longer words). The standard for communicating on the Internet is called “TCP/IP” (pronounced as TCPIP without the ‘/’) which is short for Transmission Control Protocol/Internet Protocol.
The key concept in TCP/IP is that every computer has to know or can figure out where all other computers are on the network, and can send data by the quickest route, even if part of the route is down. The reason the route is down might include a computer is shut down or a phone line disconnected or in repair. This is done by maintaining indexes of all IP addresses in a domain at multiple servers strategically spread around the country, so that messages are quickly routed along the fastest path.
TCP/IP transfers information in small chunks called “packets.” Each packet includes the following information: the computer (or last few computers) the data came from, the computer to which it is headed, the data itself, and error-checking information (to ensure that the individual packet was accurately and completely sent and received). The elegance of TCP/IP is that a large file can be broken into multiple packets, each sent over different paths in the network. These packets then re-assembled at the other end into one file and saved on the destination computer.
To access the Internet you need an Internet Service Provider or “ISP”. The ISP is connected to the Internet “backbone” which is the permanent cabling of the Internet. This backbone may consist of copper wire, fiber optic cable, microwave, and even satellite connections between any two points. To you, it doesn’t matter – the Internet’s TCP/IP works this out for you. You can connect to the Internet in one of two basic ways, dialing into an Internet Service Provider’s computer, or with a direct connection to an Internet Service Provider. The difference is mainly in speed and cost.
The above figure gives a pictorial representation of how the Internet works. You want to access a web site that is hosted on a server somewhere in the world (say the USA) and you want to access the information from India. You connect (using a computer and modem – Dial-up access) to your local Internet Access Provider, then you type in the address of your site. Your request is sent from the local ISP’s server through the different computers in the network (Internet backbone) till it reaches the server where you have hosted your site. It is like a letter traveling through the various postal networks and reaching the addressee’s place. Then the information stored on the web site that you are trying to access is sent back to your computer so that you can access it.