Hello, they are basically the same file. It is about 2 mount points directing to the same storage device and partition.
If you create something in one folder, it will show up in the other one. This also applies for deleting items.
If you delete something from the 0 folder, it will be deleted from the legacy folder. In that sense it is not a back up because any changes to one of the folders will immediately be applied to the second folder.
The items do not use more storage space (so there is no need to remove them). Effectively it is only available once, but shown twice.