You do not need to know the detailed semantics of how files are undeleted to use the Fatback program. However, if you seek a better understanding of what is involved in undeleting files and directories, then you will be interested in the information presented in this section.
All methods of undeleting presented here require the recovery of cluster chains (see File Allocation Tables, for more info on cluster chains). Recovering cluster chains is not guaranteed to give you accurate data. If another file or directory in the file system has used a cluster in the chain since the file was deleted, that cluster will no longer be valid data to recover. In order to tell if a file is able to be recovered accurately, you need to know what files are using which clusters. It is this reason that hand recovering files is not a very productive use of your time.