Remuxing moves existing encoded media tracks into a different container or packaging arrangement without re-encoding those tracks. It can change how compatible software accesses the media while preserving the encoded picture and sound. It does not solve every codec problem, because the underlying compression formats can remain unchanged after the packaging is altered.
A practical example
A workflow can place compatible video and audio tracks from one container into another that a player handles more comfortably. The picture may remain the same because the video was not decoded and compressed again during that particular operation.
A common misunderstanding
Do not expect remuxing to make an unsupported video codec playable. It changes packaging rather than decoding capability, and some track or subtitle combinations still may not fit the target container.
Related terms
Further reading
Stable technical definition. Editorial approach