The Uniform Resource Identifier (URI) is a label that uniquely identifies all resources and objects on the global web, including the protocol and service used.
A URI for an e-mail - mailto:email@example.com - has a different structure than one for a graphic on a web page or one for a file transfer - ftp:/dokumente/smtp.txt. The objects identified in the Uniform Resource Identifier can be a text file or a graphic, an Excel file, an audio or video sequence. Each individual object has its own unique Uniform Resource Identifier. The URI is identified by the protocol - http, mailto, ftp, gopher, news - by the service such as World Wide Web (WWW) and by a valid address.
A Uniform Resource Identifier or Universal Resource Identifier can be a Uniform Resource Locator (URL) or a Uniform Resource Name (URN). It identifies specific content on the Web: a sound file, a video file, an image document, or a text document. The terms URI and URL are used interchangeably. To identify sessions, a session ID can be appended to the URI identifier.