Uniform Resource Locators, or URLs, are digital addresses used to locate websites and files over the Internet and local networks. People commonly type URLs in Web browser address bars to visit websites, but URLs can also be used to connect to other networked computers. Also, people use URLs to share content with each other over the Web. URLs feature alphanumeric characters and site operators usually try to use URLs that are easy to remember.
The Protocol Section
The protocol section comes first in the URL and instructs the computer as to how it should handle the data transfer to load whatever is at the address. For example, the HyperText Transfer Protocol, or HTTP, indicates that the URL leads to a website. The Secure HTTP, or HTTPS, is an encrypted, secure version of HTTP. You may also encounter links on the Web that include the File Transfer Protocol, or FTP, that are used to transfer files between computers as opposed to websites. When formatted, protocols add a colon and two forward slashes like "HTTP://" and "FTP://."
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The Domain Name and Sub-Domain
The domain name is the host address of the website you're viewing. Domain names typically default to a site's homepage and behave like the city and state part of a physical address. For example, "eHow" is the domain name in "http://www.eHow.com." The domain name is the part people commit to memory for commonly visited websites. To complicate matters, sites also feature something called a sub-domain. This precedes the domain name in the URL. Sub-domains are like separated parts of a larger site and function similarly to multiple ZIP codes within a city. For example, "support" in "support.microsoft.com" is a sub-domain and "www" is used as a generic sub-domain in uses like "www.eHow.com."
The Top-Level Domain
The Top-Level Domain, or TLD is the suffix attached to the end of the domain name. TLDs are a bit like country codes and break up the Web so that the domain names can be reused with different TLDs. When browsing the Internet, you commonly come across the TLDs ".com," ".net" and ".org." For example, the ".com" in "eHow.com" is the TLD. TLDs can also, but don't necessarily, function as real-world country codes and reflect the website's national origin. Domain names, sub-domains and TLDs are split up with periods, referred to as "dot" in conversation.
Directory Structure and Filenames
Everything after the domain name separated by forward slashes indicate directory and filename for the Web page or data file you're accessing. The directory and filenames behave like street names and address numbers respectively. For example, the "/news/page.html" section of "http://www.fakesite.com/news/page.html" indicates the HTML-based page loaded on Fakesite.com's news directory. Links can appear as relative and absolute on Web pages. Absolute links contain the entire URL, whereas relative links only include the directory and filename section.