What is a URL? URLs explained

There are lots of things in this world that we use everyday and don’t know how they work…televisions, cell phones, microwave ovens, search engines, URLs, speaking for myself, of course. If you’re involved in online business (and if you’re reading this you no doubt are) having a working knowledge of a URL is an important tidbit of knowledge. If you’re a programmer you might just want to skip back to another post and catch up on your reading, but for those of you who may not know all the parts of a standard URL, please keep reading!

First of all, a URL is a “uniform resource locator,” and it is a way of identifying and locating items on the web such as files or pages.

Let’s look at this example URL:

http://www.blog.example.com/faq/link-policy/index.html

The http is the protocol, or method of accessing the file and stands for “hypertext transfer protocol.” Other protocols are https (secure hypertext transfer protocol) ftp (file transfer protocol), sftp (secure file transfer protocol). The portion following the protocol, www.blog.example.com, is the host, the subdomain is blog and the domain name is example.co and www indicates is an acronym for World Wide Web.

Items in the slashes, /, are directories or folders where the files you are looking for are found. /faq/ is the directory, /link-policy/ is the subdirectory, and “index.html” is the “resource ID.” This is the name of the file for the page which is stored on the specified server. /index.html is the file name for the specific page. The file name ends with a three or four letter designation of the file type like .rtf, .pdf, .jpeg or others.

If a website has a URL like this example:

http://podcast.example.co.au:80/podcastplay?id=1073682064&

the “au” is a country code and is also the “top level domain,” meaning the website originates from Australia. The second-level domain is “.co.au.” “:80″ is the default web server port. Ports may be identified in other ways but if it is 80 it is most often left out. The path is /podcastplay which is where the folder is, like in the previous example. The characters within the ? and & are a parameter. The parameter has the name id and the value 1073682064. A URL can have many parameters and they are always set off by ? and &.

A static URL is a document that can be returned by the server without the server having to do any computation. A dynamic URL, on the other hand, does require the server to perform some computation to return it. If the URL contains a question mark, it’s usually considered dynamic while no question mark in the URL usually means its static. The contents of a static URL don’t change whereas a dynamic URL is basically a template in which to display changing content, which makes updating a site much easier; Instead of changing information in the static HTML code, the content is changed in a database.

For a non-programmer, how did I do? If I missed something, join the discussion and let me know!

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