Uniform Resource Identifier (URI) - A string of characters that represents the address or location on the Internet of a particular resource or information object (piece of content). Also known as Universal Resource Identifier.

One critical component of the founding of the World Wide Web is addressability of objects. Tim Berners-Lee presented the URI as the standard for addressing objects. For completeness on this post, the other two components of the Web's success were the transfer protocol (HTTP) and the presentation language (HTML) that would allow linkages to be made among objects across the Internet.