If you’re reading this on wpxss.com, the address bar in your browser will contain the text https://wpxss.com/application/glossary/url/. That is a URL. The URL contains the protocol used to transmit information (http), the host name (wpxss.com) and the name of resource to retrieve from the host (/glossary/url/). The server that receives the request will use the name of the resource to determine what to send back, and the transmission protocol will decide how the information should be transmitted to the visitor.
In WordPress, the structure of the URLs used on a website is determined by the permalink settings.