jQuery Form Plugin: only submit certain fields

[Koroshiyasha]

OK, this is probably a really basic question, but I didn't find anything about this topic using the forum's search function. So sorry if it has already been answered.

The form plugin page states that "fieldSerialize allows you to serialize a subset of a form into a query string. This is useful when you need to process only certain fields."

http://www.malsup.com/jquery/form/#fields

My question is, what do you do with the string that the function returns you ? How do you submit the form so that only the chosen fields get processed ?

Thanks !