A URL is the address to a web page. URL is an acronym for Uniform Resource Locator.
URLs are composed of three parts. Lets use the url www.dwightwatt.com/index.html for an example
The first part comes before the first period and in this case in most cases is www. That is the name of the server the the web site is stored on. Usually people keep the web pages on a server called www but it can be any name so occasionally you will see URLs start with something different than www. If you do no enter the server name the browser will normally assume www and so dwightwatt.com also works.
The second part is the domain name which in the example is dwightwatt.com This is a name the organization has bought that makes their location unique in words on the Internet. You can but most domain names fro between 9 and 12 dollars a year. The first part is the specific domain and the second part is supposed to tell us about the organization but in many cases is not enforced. .com is supposed to be commercial businesses, .org supposed to be non profits, .gov is government organizations and .edu is post secondary colleges
The third part is the /index.html in our example. This tells which specific page on the web site we want. The entry page to a web site is usually inex.html or index.htm and is usually left off. If you wanted to go to a specific page on a web site you would include the folder and name of the file here
Thanks Tony for question