A URI is a Uniform Resource Identifier, an Internet protocol element consisting of a short string of characters that conforms to a certain syntax. The string comprises a name or an address that can be used to refer to a resource. It is a fundamental component of the World Wide Web.
Examples of URI's are HTTP, FTP, mailto, etc. URI's are defined by IANA, and their full list can be found here.
The telnet protocol uses the registered URI "telnet", described as "Reference to interactive sessions". For example:
Uri is also one of the cantons of Switzerland. This is its coat of arms:
