Postbacks are the primary way in which data is submitted to the server. Field values can be retrieved in postbacks with the use of the wf:q/1 function call along with its siblings, wf:qs/1, wf:mq/1, wf:mqs/1, wf:q_pl/1, and wf:qs_pl/1.

Unlike HTML, you don't have to worry about adding <form> tags - an element's ID is used.