Forms
Some WAP sites require the user to send information to the server. This is usually for personalization, data collection or searching purposes.
Due to the small screens cellphones have, a trick is to put the form itself on the first card, and info on how to use the form on a second "help" card.
This ties the ever-important help information to the form without requiring an extra data fetch.
Card: One part of a WML deck (or file) that is displayed at a time. Switching between cards in a deck is fast because the whole deck is already loaded.
Form: a series of related inputs you (the user) need to fill to send data to the web server. The form itself will explain what info is required.