When a browser form is submitted to the server, the named input boxes are also submitted with the data they contain. The submitted data is in name/value pair format for each of the input boxes on the form. The server can then process the submitted values and produce the result page.
When a WEBROUTINE page is presented in the browser, that page has input boxes (or other more complex controls) for each of the fields in outgoing WEB_MAPs. Each input box uses the same field name on the form as the field name in the WEB_MAP. (No prefixes are used.)
When this page is submitted to another WEBROUTINE, the WAM runtime assigns the input values to the fields specified in that WEBROUTINE's incoming WEB_MAP statements based on the field names that match the name of the input box. Hence, the posted values are assigned to appropriate fields and are available once the WEBROUTINE begins execution.