The Internet has become such a normal part of our daily lives that it's hard to imagine a time when it wasn't there. We use it so much we forget to ask the obvious: What exactly is it?
The simplest definition of the Internet is that it's a network of computer networks. A computer network is a group of computers connected to each other so they can easily communicate and share files and resources (such as printers and scanners). Many organizations and businesses have networks that connect offices all over the country and world.
The Internet is the World's Largest Computer Network.
It connects networks all over the world. At its heart is a backbone of high-speed data communication lines through which any connected computer can trade information with any other connected computer.
One of the most remarkable things about the Internet is the wealth of information it puts at your fingertips. It's an incredible fountain of knowledge fed by sources all over the world. You can find everything from information on the latest cancer research to strategies for beating the latest computer game. The information never stops, either. New pages are being added daily. The price of admission? A computer and an Internet connection through an Internet service provider (ISP).
Lesson 1: The World Wide Web
Right now you're using a special part of the Internet. It's called the World Wide Web (or just the Web, for short). The Web is what made the Internet so popular. Until the Web was created, the Internet was black and white and not read all over. Pages were text-only, with no color or graphics of any kind. It was great for scientific reports or government documents, but not for shopping for the latest CD from your favorite band or finding images for a school report. Consequently, the Internet was used primarily by scientists and engineers.
In 1989, Tim Berners-Lee, an Oxford-trained computer scientist, had an idea for a "global hypertext project." To make his idea a reality, he developed new ways to navigate the Internet with a computer language called Hypertext Markup Language or HTML.
Hypertext is a different way of moving through information. Instead of reading text from beginning to end, you interact with it. You click a link and suddenly you're not moving through the text from start to finish like you would in a book or a magazine article. Instead, you're making a quick side trip or jump.
HTML is more than just hypertext, though. It's also a markup language—a system of codes for how a computer should display text and images on a screen. Markup languages also determine how a computer should react to actions you make such as pressing a key or clicking a mouse button. What made HTML such a perfect markup language for the Web is that it can be read by many types of computers and is very economical. It allows Web designers to create graphically rich Web pages that are small in file size. Small file sizes are important on a network like the Web because they are faster and easier to exchange over the thousands of miles often separating computers.
With the creation of HTML, the Web was born. HTML made it easy to create Web sites like this one that have images, videos and even sound. The small file allowed them to be quickly communicated over the Internet. Suddenly, everyone saw the potential of the Web as a global communications system and wanted to get on it. The Web grew rapidly. Today, millions of people access the Web daily for news, entertainment, shopping, education and business.
Lesson 2: What is a URL?
Click inside the address bar below to explore the different parts of a URL in this example.
Your home has a unique address. Give anyone in the world your address and (given enough time and money) they could arrive on your doorstep.
Web pages need unique addresses too. These addresses allow you to find a particular page, as well as direct others to it. Giving each page a unique address is no easy task. The Internet is a network of networks, many of which are growing rapidly. In fact, new Web sites are added daily, each page in the site needing its own address. It's like having entire neighborhoods built in a day and each home needing an address immediately. That means a lot of naming and numbering, especially when you consider there are already billions of pages on the Internet that have already used up billions of names. Fortunately, there are enough parts to a Web address that it's fairly easy to create new ones.
The technical name for a Web address is URL, an acronym for uniform resource locator. Look at the top of your browser right now and you can see the URL for this page. It starts with http://. You've probably typed in a URL before to get to a particular Web page. Let's examine each part. We'll use for our example the URL for the Web site of the National Aeronautics and Space Administration—http://www.nasa.gov.
Lesson 3: How Information Travels on the Internet
When you connect to a Web site through an ISP and start exchanging information, there isn't a fixed connection between your computer and the Web server computer hosting the Web site. Instead, information is exchanged using the best possible path at that particular time. Special computers called routers determine these paths, avoiding slow links and favoring fast ones.
Lesson 4: Breaking Messages Into Packets
A page on the Internet—whether it's full of words, images or both—doesn't come to you in one shipment. It's translated into digital information, chopped into pieces called packets, and sent to you like a puzzle that needs to be reassembled. Web pages are broken down this way because small pieces can travel faster and make the most efficient use of the Internet's resources. Instead of waiting while a long train of information goes by, packets can just fit in wherever and whenever there is space in a wire.
Each packet has its part of the data, plus additional information needs to be routed to the destination and reassembled with the rest of the packets. Reassembling is important because the packets do not necessarily arrive in the same order in which they were sent. Packets can get jumbled during transmission and occasionally even take different paths. Devices called routers determine the most efficient path at the time the packets enter Internet traffic. This helps prevent traffic jams and makes the Internet more efficient. When the packets arrive at their destination, your computer discards the addressing information and puts the packets in the proper order to reassemble the information for you. Once all the packets are reassembled, the complete page appears on your computer screen.
Try Activity 1: Packing a Message ›
Lesson 5: Bigger is Better
In Bandwidth, Bigger Is Better
Ever had to wait 10 or more seconds for a Web page to finish building on your screen? That can be a combination of many things. First, the file size of the Web page was probably big. There was a lot of information to get through. Second, the computer you were using may have a slow microprocessor. A fast microprocessor can process incoming information faster. Third, your connection to the Internet may have been slow. For better performance, the connection you were using needed more bandwidth.
Bandwidth is the amount of data that can pass through a particular connection in a set amount of time. It can differ depending on what type of connection your computer has to the Internet. The greater the bandwidth of the connection, the faster a Web page builds on your screen. Faster bandwidth means files download faster and videos like the one on this page play quicker and more smoothly.
When the Internet was largely text and fewer people used it, bandwidth wasn't that important. Text pages have small file sizes. But today there are many more people on the Internet and we use it to exchange photographs, download software, listen to music, and even view movies online. These kinds of files are much larger and require a bigger connection to your computer to perform properly. That makes bandwidth very important.
Lesson 6: How Computer Speeds are Measured
Bandwidth is measured by the amount of information that can be transmitted per second. The measurement used is bps, and is the smallest unit of information handled by a computer. In its digital form, it's a 1 or a 0. Bits don't mean much by themselves, but in groups of eight they form bytes that can be used in various combinations to represent letters and numbers.
Today's connection speeds to the Internet are measured in Kbps (kilobits per second) and Mbps (megabits per second).
1,024 bps = 1 Kbps
1,048,576 bps = 1 Mbps
That means a 56 Kbps connection under ideal conditions can transfer 57,344 bps (56 x 1,024 bps) from the Internet to your computer. In reality, most 56 Kbps connections transfer around 48,000 bps.
How Bandwidth Translates Into Speed
Maybe you have gone to a network Web news page like abcnews.com. You have probably used an optical disk with a computer. This activity lets you compare connection speeds to see how much difference a fast connection can make when you are trying to download something from the Internet.
For reference, try three different file sizes. Enter 100K, the approximate size of a typical news Web page. Then try 5MB, the size of a video clip. Finally, try 640MB, the size of an optical disk.
You probably do not download an optical disk every day. That's the equivalent of 150,000 printed pages. But the faster your connection, the better the performance you will experience for doing things like viewing movie clips or downloading computer games.
Lesson 7: Information on the Internet
One reason the Internet has so quickly become a part of our daily lives is you can do practically everything on it. You can listen to music, play games, send email, chat, shop, and of course, use it to do research and homework.
But how good is the information on the Internet? The information can be excellent. It can be poor. It can be anything in between.
Anyone can put up a site on the Internet. That's one of the great things about the Web. It's also why you have to be careful. There is no editorial review board, no information fact checker, no quality control expert. You have to be your own judge on the quality and validity of the information you receive.
What about when you use a search engine? Here you have to be careful, too. Most search engines use the location and frequency of keywords as the basis for ranking responses to a query. In other words, they don't rank the pages by the quality of information, but primarily by where and how often the words in your query appear. Some search engines give an extra boost to pages that have lots of links to them from other Web pages. Some give extra weight to pages frequently clicked on by people doing similar searches.
Search engines are useful, but they miss a lot of information. Most have access to less than one percent of the content that exists on the Web. Billions of pages are not even considered. New specialized search engines are popping up that focus on specific areas such as news, law, or even shopping. By specializing in a specific area, these search engines answer queries with many pages that traditional search engines would miss.
What can you do to be a savvy Web user? Pay close attention to the source of any information you find on the Web. For instance, for facts on ancient Egypt, a site created by National Geographic will be more reliable than a site put up by someone who's writing about their vacation at the pyramids. Another trick is to not rely on just one source, but use several.
Lesson 8: Connecting Wirelessly
One of the fastest growing ways to access the Internet is to use a wireless connection. Wireless cards come built into many computers or can be plugged into one of the slots on many machines. Regardless of which device you use, wireless connectivity allows you to move about a room or even a building and still be connected to the Internet.
There are many types of wireless devices. Many use acronyms and have unique names, but each offers wireless connection at a variety of speeds and distances. They can allow you to connect to the Internet from ranges of 30 feet to 30 miles away from an access point.
A wireless diagram explains how WiFi works to connect many devices to the Internet wirelessly.
Explore these links to learn more about wireless networks.