What’s different between URI, request-URI and URL?

The URI standard is STD 66, which currently maps to RFC 3986.

URI vs. URL

Section 1.1.3 describes the difference between URIs and URLs (and URNs).

Components

Section 3 describes the components a URI can have.

For the URI http://www.example.org:56789/a/b/c.txt?t=win&s=chess#para5 these would be:

• Scheme: http
• Authority: www.example.org:56789
• User Information: not present
• Host: www.example.org
• Port: 56789
• Path: /a/b/c.txt
• Query: t=win&s=chess
• Fragment: para5

request-URI

The term “request-URI” is not defined or even used in STD 66 / RFC 3986.