Intercompany Balancing Rules use cases and how to use them?

Hello,
I went through with the oracle Document (Implementing Enterprise Structures and General Ledger) explaining intercompany balancing rules with the examples but i could not seem to understand how Ledger Rules and Legal entity rules work, so i would like a use case for them if possible.
I understand for the primary segment rules we use them for primary balancing values under one ledger and chart of account rules are used to also balance primary balancing segments but i dont know how to use legal entity rules and ledger rules.

Thank you.