what is difference between url uri and urn code example

Example: difference between URI and URL

The terms “URI” and “URL” are often used interchangeably,
 but they are not exactly the same.

1.A URI is an identifier of a specific resource. Like a page,
 or book, or a document.
2.A URL is special type of identifier that also tells you how to 
  access it, such as HTTPs, FTP, etc.—like https://www.google.com.
3.If the protocol (https, ftp, etc.) is either present or implied for
 a domain, you should call it a URL—even though it’s also a URI.