Đại Diện (Proxies)
Proxies were the historical way in Blender to allow some local editing of linked data-blocks. This was mostly aimed at character animation.
They are now fully deprecated as of Blender 3.0, replaced by the new Library Overrides.
Existing proxies in older blend-files will be converted to library overrides when opening it in Blender 3.2 and later.