How to manage multiple companies within the same site, like a Group of Companies

Install / Update Setup
1

Hello,

How to manage two or more companies as a single site ? Please elaborate.

2

here is a example
https://erpnext.org/docs/user/manual/en/setting-up/users-and-permissions?

3

https://erpnext.org/docs/user/manual/en/setting-up/articles/managing-multiple-companies?