-This optional file, which resides in the rootfs system, not in the live media as above mentioned files, if exists will be used as a list of directories which not need to be persistent and which their content does not need to survive reboots. This is achieved by bind mounting for each directory listed there a tmpfs on the original path. This will permits to save precious writes and speed up operations for content like web caches and temporary files (like e.g. /tmp and .mozilla) which are regenerated each time.
+This optional file (which resides in the rootfs system, not in the live media)
+is used as a list of directories which not need be persistent: ie. their
+content does not need to survive reboots when using the persistence features.
+
+This saves expensive writes and speeds up operations on volatile data such as
+web caches and temporary files (like e.g. /tmp and .mozilla) which are
+regenerated each time. This is achieved by bind mounting each listed directory
+with a tmpfs on the original path.