When you specify a URL in a web browser, the intent is usually to fetch a document from a remote web server.
To call up the debugger console
To interactively execute statements
As document source
The view-source: URL can be used in Netscape to call up a source view of a document under script control. Its not very portable and not much use for anything other than debugging.
These are all described in separate topics.
This technique does not work with MSIE 3.0.