The "Sticky Bit" is a permission bit that can be set on either a file or a directory.
If it is set on a file, then that file will remain in memory after execution, thus ?sticking? in memory. This is useful when running a multi-user program (such as a bulletin board system that I ran once) to make the program execute faster for the next user. This was a common programming tactic earlier in the history of computer programming when speed and disk space were at a premium.
If the sticky bit is set on a directory, only the owner of files in that directory will be able to modify or delete files in that directory - even if the permissions set on those files would otherwise allow it.
It executes from user and behaves as it executing from the root.