You can store backups of each of your files separately, or you can store them in an archive with other files that you're backing up.
Files stored in an archive can be more readily identified as belonging to a certain time or machine (by naming the archive), more easily transferred in bulk to other systems (by transferring a single archive file), and can sometimes be more readily compressed than individual files can.
You have several archive formats to choose from under Neutrino, including pax, and tar. Neutrino also supports cpio (*.cpio), but we recommend it only when the archive needs to be readable by other systems that use cpio archives.