URI (Uniform Resource Identifier) is a superset of URL. URI provides a simple and extensible means for identifying a resource in a more generic way. For example, the following strings are all valid URIs:

ftp://ftp.is.co.za/rfc/rfc1808.txt

http://www.ietf.org/rfc/rfc2396.txt

ldap://[2001:db8::7]/c=GB?objectClass?one

mailto:John.Doe@example.com

news:comp.infosystems.www.servers.unix

tel:+1-816-555-1212

telnet://192.0.2.16:80/

urn:oasis:names:specification:docbook:dtd:xml:4.1.2

When an XHTML document is published on the Internet, its location can be represented by a URL, which is also a URI.