A string of characters used to identify a resource on the internet, typically consisting of a protocol (such as HTTP or FTP), a domain name, and a path to the resource.

"The URI 'https://www.example.com/index.html' identifies a web page on the example.com domain."

A string of characters that unambiguously identifies a particular resource.

"URIs enable the identification of resources on the internet or within a network, such as web pages, documents, and images"