system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What does it mean when a song/album is remastered and how is it done?
gpt
When talking about recordings on Vinyl, the initial "Master" copy of the vinyl will be of the highest quality, every subsequent copy will be of lesser quality due to things like dust, scratches and what not that each get passed down to any subsequent copies of that copy. And the degradation that happens to a disk when pressing a copy of it.

To mass produce records the initial "Master" copy will be used to make actual 'production' masters that are used to make the full order of discs. So for instance, there may be one "Master" which is used to make six Productions Masters that then are used to make a thousand copies each for a total of 6000 records even though the "Master" was only pressed 6 times, thus preserving it's quality as much as possible.

When a record is "Re-Mastered" it (sometimes) means that a new production master is made from the initial Master. A similar thing happens with physical film when it is copied.

Modern re-masters can mean many different things though, since most media has gone digital, sometimes a remaster is the re-conversion of a record or movie using higher quality digital formats (e.g. blu-ray or 4k, or at a higher sample rate for audio). This kind of remaster only really applies to things that were originally recorded on analog media, and aren't as easy for things that were filmed or recorded digitally from the start (if the quality was low to begin with). In other instances a "re-master" may refer to cleaning up source material to "fake" a better quality using things like digital noise reduction.