The server resource name is called a uniform resource identifier, or URI. URIs are like the postal addresses of the Internet, uniquely identifying and locating information resources around the world. URIs come in two flavors, called URLs and URNs.
The uniform resource locator (URL) is the most common form of resource identifier, and URLs come in two flavors: absolute and relative.
Most URLs follow a standardized format of three main parts:
• The first part of the URL is called the scheme, and it describes the protocol used to access the resource. This is usually the HTTP protocol (http://).
• The second part gives the server Internet address (e.g., www.joes-hardware.com).
• The rest names a resource on the web server (e.g., /specials/saw-blade.gif).
Today, almost every URI is a URL.
The second flavor of URI is the uniform resource name, or URN. A URN serves as a unique name for a particular piece of content, independent of where the resource currently resides. These location-independent URNs allow resources to move from place to place. URNs also allow resources to be accessed by multiple network access protocols while maintaining the same name.