Attachments, embedded docs, and images - here's what you need to know about parent-child relationships between documents.
Introduction
Families are the relationship between a parent document and its children.
Parents, Children, and Standalone Documents
Parent document: documents that include/have attachments/embedded files.
Child/Children document(s): documents that are attachments/embedded files. For example, an email with attachments: the email would be the parent document, and the attachments would be its children.
Standalone documents are those that do not have any attachments/embedded files.