The different parts of a URL determine the mapping to a CSP page:
Web Server. This is the name or IP address (127.0.0.1:57772, for example) of the Web Server.
Virtual Directory and Application Path. In a default configuration, the second part defines both a virtual directory on the Web server and a Caché application path. Both are configurable.
CSP page name. This is the name of the requested CSP page. The name must have either a .csp or .cls extension.