HTML Uniform Resource Locators

A URL is another word for a web address.
A URL can be composed of words address. Most people enter the name of the website when surfing, because names are easier to remember than numbers. Web browsers request pages from web servers by using a URL. When you click on a link in an HTML page, an underlying 'a' tag points to an address on the world wide web. A Uniform Resource Locator (URL) is used to address a document (or other data) on the world wide web.

Explanation:

Scheme - defines the type of Internet service. The most common type is http.
Host - defines the domain host (the default host for http is www).
Domain - defines the Internet domain name.
Port - defines the port number at the host (the default port number for http is 80).
Path - defines a path at the server.
Filename - defines the name of a document/resource.