title: What is the difference between URI, URL and URN?
body: <p>What's the difference between an URI, URL and URN? I have read a lot of sites (even Wikipedia) but I don't understand it.</p>
  
  <p>URI: <a href="http://www.foo.com/bar.html" rel="noreferrer">http://www.foo.com/bar.html</a><br>
  URL: <a href="http://www.foo.com/bar.html" rel="noreferrer">http://www.foo.com/bar.html</a><br>
  URN: bar.html</p>
  
  <p>Is this correct?</p>