A button form item, as the name implies, consists of a button that does a custom action. You can customize the button's appearance and position on the form.
An empty item used to add a space between neighboring items.
A simple form item is an editor-label pair usually bound to a formData object field used to display and modify this field.
You can also create a simple item without binding it to a formData field. For example, it can be a check box that allows a user to confirm his agreement to process entered data.
For detailed information on configuring simple items, see the Configure Simple Items topic.