Hmm, I would probably say automation rule, just because I am passionate about reducing the amount of manual tasks.
I think the preference page is a feature that provides value to customers, potential customers and us as a company.
A visitor is an anonymous visitor to the web who has accepted cookies while a prospect is an identified person. And by identified, I mean that the person has provided their email address through, for example, a form.
Form is a form hosted by Pardot. Form handler is a link between a custom form and Pardot.
A submission is when a person fills in a form that is linked to Pardot. A conversion is when an anonymous visitor provides their email address and converts to a prospect, usually also through a form.