Yup, it just re-compresses the photos to save some space potentially sacrificing the quality of originals. Nothing to do with the backing up the files securely.

Yup, it just re-compresses the photos to save some space potentially sacrificing the quality of originals. Nothing to do with the backing up the files securely. And also not something any photographer would ever do to photos, but I guess it can be useful when you have tones of holiday snapshots where maximum quality or ability to edit raw photos in future is not a concern.