CAUTION:
The Related tab is displayed when an action requires related document to be configured. The Related tab allows you to configure how related documents are defined. If the primary document also meets the requirements of a related document, the primary document is excluded from related documents results.
Note:
When a Workflow rule evaluates related documents, as soon as the rule encounters one related document that evaluates True for the rule's condition, the rule evaluates as True and the True logic is executed. If all related documents evaluate to False, then the False logic is executed.