Clarification on Business Rule Scope of "All Forms"

My analyst brain is struggling to understand what "All Forms" scope on a Business Rule really means.  Is it:

1. The fields referenced in the business rule must exist on *all* forms (including Quick Create), even if the user is viewing the Main form in order for the business rule to work, or 
2. Th fields referenced in the business rule must exist on the form the user in viewing in order for the business rule to work.