[Adoby]

Sometimes the original folders and filenames store important information. There may be some form of tree structure where the names of the folders are used to specify things like genres, locations, times, series, authors, versions and so on. It is possible that this information doesn't exist anywhere else. And calibre can't scan folder names to add as metadata when adding books. And calibre can't read metadata, when adding the book, both from the filename and from inside the book. It is either or.

After adding books to calibre you should always immediately examine the newly added books in calibre to ensure that they have correct and complete metadata, and possibly add metadata that was encoded in filenames and the folder structure that is used to store the original book. And obviously you need to do this before you delete the original books, if you don't want to loose important information. Calibre unfortunately doesn't remember then original filename and path of the books that are added.

And, like itimpi says, it still is a good idea to keep the original books as a backup against disaster, or in case you missed to record some important information in the metadata when the book was added. But you could for instance zip and move away the originals to "archive" them somewhere else. Preferably on another disk than the one used by calibre, and preferably even in another location, just in case. The copies of the books that was added to the calibre library, along with the metadata that was registered from the originals, will be what is used by calibre.

As has already been said, Calibre doesn't keep track of the original filenames and paths from the original books. That is sometimes a pity. For some that would have been a nice feature to have. It would have reduced the risk of loosing information while adding the books, and also might have made it easier to locate the archived originals sometime in the future.

But information about when the book was added is recorded, and this can make it easier to locate the archived originals. Especially if they are stored in a folder or zipped archive with a timestamp that is close to when the book was added to calibre.