These are the original texture WADs used in the development of the Quake missionpacks. They were pulled from the Quake Remaster on Steam, where they were left apparently accidentally. They include many textures that weren't used in the original games.
The WADs marked as "reconstructed" were assembled from the BSP files that internally used those WADs. The WADs marked as "original" are the genuine versions that the mappers on those projects used.
You can find out which maps used which WADs in this post.
The WADs marked as "reconstructed" were assembled from the BSP files that internally used those WADs. The WADs marked as "original" are the genuine versions that the mappers on those projects used.
You can find out which maps used which WADs in this post.