Relationship between URL and URI

URL and URI The difference between

Titles we often encounter URL and URI Two words , But it's hard to figure out the relationship between the two ？

• What is? URI？ Uniform resource identifiers . The name of a resource in the network . But by URI Can't locate resources .
• What is? URL？ Uniform resource locator . Represents a resource in the network , meanwhile , adopt URL You can locate the resource .
• URI and URL What is the relationship , What's the difference? ？
  • URL Include URI
  • http://localhost:8080/servlet05/index.html This is a URL.
  • /servlet05/index.html This is a URI.