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It will go to the form's ACTION (which is process-order.php).
That is, the file actually contains the HTML form that retrieves user input.
(Remember, you can use ASP to interact with client-side scripts and HTML.
Using this method of processing and validating user input can greatly enhance the usability and responsiveness of your Web-based forms.
For example, by placing error information adjacent to the form field where invalid information was entered, you make it easier for the user to discover the source of the error.