URL is an acronym for Uniform Resource Locator and is a reference (an address) to a resource on the Internet.
A URL has two main components:
Protocol identifier: For the URL http://example.com/foo, the protocol identifier is http.
Resource name: For the URL http://example.com/foo, the resource name is example.com.
example.com 是为了connection，而foo是个path，它才是request的对象
Reference:
https://en.wikipedia.org/wiki/URL
https://docs.oracle.com/javase/tutorial/networking/urls/definition.html
https://en.wikipedia.org/wiki/Query_string
