The relationship type between accounts and contacts is a lookup relationship. A lookup relationship
links two objects together, but does not affect security, ownership, or deletion. A master-detail
relationship is a type of lookup relationship that creates a parent-child relationship between two
objects, where the child records inherit the security and ownership of the parent record, and are
deleted when the parent record is deleted. A self relationship is a type of lookup relationship that
links an object to itself, creating a hierarchy of records.
