Form modification is the process by which data entered by a user

[adakist]

Form modification is the process by which data entered by a user is translated into another format before being submitted to the form's server.

[brumbino]

When data from a form is submitted to its server, the data has to be formatted in a way that the server can understand. The format is usually in the form

<url>?<field1=value>?<field2=value>...

where <field1>, <field2>, and so forth are the NAME attributes of the INPUT, SELECT, and TEXTAREA elements of the form. The values are, with minor translations made by the browser, the VALUE attributes of those elements.