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The closer term within Marketo is "AutoFill", not "Pre-Fill."
They both are variations of filling out form fields without user intervention, but AutoFill specifically allows for query parameters (such as the mktg_medium, mktg_campaign, etc. used here) to fill in fields.
However, AutoFill only works out-of-the-box for hidden fields: you can add a Hidden type field to your form and then you'll see the AutoFill option at the lower right, where you can pick a query param to act as a data source.