Are you referring to this question?
We have several moderators but everyone in the forum is allowed to ask or answer others questions
All of the above can happen.
It depends on what your app does.
Facebook, users update their own data, but Facebook doesn’t need to go in and approve each individual post. And then this data is fetched in other devices for people to see
Apple has a user facing store app, where users can see their order status. But another internal app where employees can scan packages and update that their package arrived at the store. This then updated the user their package is at the store
Facebook Marketplace has the normal tab for you to view items for sale, but if you went further you can post your own items to sell, by saying you’re a seller
When you post an item others can see it