The URL, or Uniform Resource Locator, is the address for a particular file on the World Wide Web. Each URL has components that let your computer find the file that you're looking for, whether that file is located right around the corner or on a server in Timbuktu. Let's start by looking at the components of a sample URL:
Working our way from left to right, the first part of the url is:
This portion tells your computer what protocol to use when connecting with the site. Most websites, including this one, use HyperText Transfer Protocol, or http for short. Having the correct protocol listed ensures that your computer and the server hosting the website are literally speaking the same language.
Other protocols you might see listed in a URL include https (an encrypted version of http that is used for secure sites, such as ecommerce sites), ftp, and telnet. If you enter a URL and don't include a protocol, the computer will use http by default.
The next part of the URL defines the file host:
The www portion indicates that this site is located on the World Wide Web. This is the most common prefix to a host name and if you don't enter a host prefix, the computer will use www by default. If the prefix is anything other than www, it usually indicates a subdomain – essentially a domain within a domain. Webmasters often set up subdomains when they want to separate a portion of their site and make it distinct from the rest. For example, you could also reach this article through the html subdomain of bellaonline:
The middle portion of the host, the domain name (in this case, bellaonline) tells your computer who is hosting the file you're looking for. In order for a file to be available on the World Wide Web, someone has to put it on a computer, generally a specialized type of computer called a server, and hook the computer to an internet connection. Your computer can look up the domain name and use it to locate the server that is hosting the desired file.
The last portion of the host name (.com in our example) is the root domain. The root domain tells you what type of organization is hosting the site. Commercial websites will use .com or .net, or occasionally .biz; schools will use .edu; non-profit websites are typically found at .org; and governmental websites use .gov.
Every part we've looked at so far tells your computer how to find the server that's hosting the file you want to look at. Now that you've located the correct server, the rest of the URL (everything to the right of the root domain) tells you where exactly the file is within the server.
If you have a filing cabinet in your office, you probably use it to store your files inside file folders. A computer stores its virtual files in much the same way, using folders to keep its files organized and make it easy to quickly locate a particular file. Going back to our example, this file is located within the 'articles' folder on the www.bellaonline.com server. You can tell which parts of the URL are folders because they're always separated from the rest of the URL by a single slash (/).
The final part of the URL (art23821.asp) is the actual file name. The left part of the name is assigned by the file's creator, and the right part (.asp) is the file extension. This tells your computer what type of program to use to open the file. For example, if your file had a .doc extension your computer would open Microsoft Word to view it, while a .html file is typically viewed in a browser such as Internet Explorer. In this case, .asp informs your computer that this file is a webpage that contains code from the programming language ASP.