DISCLAIMER: All this is WIP!
Override is a generic term used to design the usage of a reference data, with some local modifications to it.
- When the reference data changes, those changes also get applied to its overrides, as much as possible.
- A reference data can be used by several overrides at the same time.
In Blender currently we have Library Overrides, designed to replace and extend the possibilities of the old proxy system.
A future idea is to also have 'Dynamic Overrides', that could be used on local data as well.