Only available for signup forms. Used to specify the placement of the labels when the form is rendered. In general, this is discouraged, but it is available for minimal presentations for quick email signup forms.
inline- sets the labels as the HTML5 placeholder attribute on the input.
above- displays form labels above the form fields with a tag
Note, the rationale here is that, while labels being above or beside the input can be altered with CSS, making them appear as placeholders is more complicated.
Example, to have labels appear as placeholders:
<div class="ngp-form" data-id="12345" data-labels="inline"></div>