URL

http://www.questionat.com
An internet address of a website, file, or document in the general format
http://www.questionat.com/directories/filename
Every computer connected to the internet has its unique web address, without which it cannot be reached by other computers.
Also called universal resource locator or Uniform Resource Locator (URL).

A typical URL has the form http://www.questionat.com/index.html, which indicates the protocol type (http), the domain name, (www.example.com), and the specific web page (index.html).

The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web. Hypertext is structured text that uses logical links (hyperlinks) between nodes containing text.

Canonicalization is the process of picking the best url when there are several choices, and it usually refers to home pages.