A Uniform Resource Locator, or URL, is web-speak for address. It is the address of a web page and contains several elements. An email address identifies an account on a mail server. Quite often an email server has the same domain name as the web site. The major difference between a URL and an email address is that the email address always has an "at"sign ("@") and a URL never does.
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A URL has three main elements: a protocol identifier, a domain name and a file and path structure. For example, in "http://www.something.com/here/what.html"the "http" is the protocol identifier, "www.something.com" is the domain name" and "here/what.html"is the path and file name. The protocol identifier tells what transfer protocol or language is in operation to carry the file. The domain name is the name of the web site. The file is the page the user wishes to see and the path is the directory on the web server where the file is located.
An email also has a domain name. However, the domain name does not have "www"in front of it. The domain name is preceded by a user name and the two parts of the email address are separated by "@." So an email address looks like "email@example.com."
Some email accounts are easy to confuse with web addresses. Web addresses don't always have "www"at the beginning. The site's owners can create subdomains. These give an address that seems to be a root directory of a web site, but actually points to a subdirectory. Mail.yahoo.com is a subdomain of www.yahoo.com and so looking for the www is not always a reliable indicator that the address is a web site. Email addresses can also contain dots and so "firstname.lastname@example.org" does look like a web address. The tell tale sign is the "@." It is also confusing that email servers use the same domain name as the web site with which they are associated. "email@example.com"is an email address, but "news.bigtv.com"is a subdomain, and therefore part of a URL.
Email addresses are much older than URLs. In fact, email addresses are older than the Internet. The first email system was written by Ray Tomlinson in 1971. The addresses for this email system included the "@"symbol still used today in emails. The URL was part of the work performed by Sir Tim Berners-Lee when he created the World Wide Web in the early 1990s. The definitive document on the structure of a URL was written by him and published in 1994 by the Internet Engineering Task Force.
Although both URLs and email addresses look similar, they are handled by different types of applications. Emails are passed over the Internet by mail agents. The journey of an email is governed by the Simple Mail Transfer Protocol. Email programs know not to send email to web servers, but to mail agents. Web browsers do not talk to mail agents, but to web servers.