sbin directories contains programs which are generally system administration only. Programs for regular users should never go in them.
A few programs are needed during startup, and end up in
/sbin/. These must be available before file systems are mounted. Things like
fsck that are required to check and mount files systems must be there.
Most packaged programs end up in
/usr/sbin/. These may be on a file system other than the root file system. In some cases they may be on a network mounted drive.
Local programs and scripts belong in
/usr/local/sbin/. This identifies them as clearly non-standard, and possibly only available on site.
For further explanation try running the command
man hier which should provide a description of the recommended file system hierarchy for your distribution. You may also want to read about the File System Hierarchy on Wikipedia