Through the Internet people can:ne computer by itself is a useful tool. You can work with and store a great deal of information. A network, or group of computers working together, is an even greater tool. You and other people can share and work with each other's information in a variety of ways. If a network can exchange information with other networks through a protocol called TCP/IP, it is part of the Internet. At its simplest, the Internet is a network of networks. No one person or company runs the Internet. Because of this design, the information available on the Internet changes constantly, and new computers are continually added to the network, which provides an ever-growing source of information.
A protocol is a set of rules that computers use when exchanging information with each other. The basic protocol for the Internet is TCP/IP.
A company can maintain an internal network of web sites, email, and other Internet services; this structure is called an intranet. An intranet is a particularly useful way to disseminate information within a company. Intranets can contain such information as benefits policies, sales and marketing product details, company phone lists, product plans, and online forms.
Usually, an intranet is kept separate from the Internet by hardware and software called a firewall, so that only people in the company can access that intranet.
When a company extends its intranet outside the firewall to allow customers, suppliers, and offsite workers access to the company's data, that structure is called an extranet.
TCP/IP is the middle layer in Internet communication, and it specifies exactly how all digital data is transferred from one computer to another. The next layer above might be HTTP (HyperText Transfer Protocol), which specifies what type of communication and information is sent between a web site and a web browser. HTTP is what makes web servers and web browsers speak the same language; TCP/IP is what makes sure the messages are sent back and forth reliably.
Other protocols that work "on top" of TCP/IP include:
Most files on the Web have the extension html or htm. HTML stands for HyperText Markup Language.Because the protocol for accessing the web is HTTP, all web URLs begin with http://, as in the preceding example. The rest of the example URL is straightforward--the computer hostname is www.danishfurniture.com, the directory on that computer is products, and the file in question is orderform.html. Typing that URL into Navigator's Location field displays the file orderform.html, from www.danishfurniture.com, in the products directory. The file is sent from the server to the client through HTTP.
NoteOn the Internet, a computer is identified by a number, such as 198.95.251.30. This number is called a computer's Internet Protocol address, or IP address. To make Internet navigation easier for humans, each IP address is also associated with a hostname, such as home.netscape.com, or www.danishfurniture.com. The words you type into the Location field in Netscape Navigator are automatically translated to IP addresses by a special program called the Domain Name System (or DNS), which is maintained by your Internet provider or information systems department.
Sometimes the word server is used to mean the machine that serves the documents, but in these discussions, server refers to the installed program.When you install a Netscape server, you specify a directory to contain all the files you want to serve to clients. All directories and subdirectories below that main content directory are available to clients. As mentioned previously, the most common type of content at a web site is HTML files. Graphic images and sounds are also often available on web sites. Additionally, web sites can contain programs that perform special tasks. For example, a web site might have a program that looks up stock prices, based on information a user fills out in an HTML form. Further, some web sites can hold programs that actually run on client computers, when they connect to the server.
The uses and abilities of web sites are virtually limitless. As the definition of HTML grows, so does its ability to present more varied and dynamic information. And with Java, the programming language that was created to run programs over the Internet, you have the power to make a web site into almost whatever you want. On the web you can find shopping malls, interactive stories, encyclopedias, video games, banks, and much more.