Example stolen from here (where there is also a description of the differences):
URL http://www.pierobon.org/iis/review1.htm
URN www.pierobon.org/iis/review1.htm#one
URI http://www.pierobon.org/iis/review1.htm.html#one
Example stolen from here (where there is also a description of the differences):
URL http://www.pierobon.org/iis/review1.htm
URN www.pierobon.org/iis/review1.htm#one
URI http://www.pierobon.org/iis/review1.htm.html#one