A URL will often comprise a path, script name, and query string. The query string parameters dictate the content to show on the page, and frequently include information opaque or irrelevant to users—such as internal numeric identifiers for values in a database, illegibly encoded data, session IDs, implementation details, and so on. Clean URLs, by contrast, contain only the path of a resource, in a hierarchy that reflects some logical structure that users can easily interpret and manipulate.