Simple definition
On shared Unix directories, the sticky bit generally restricts file deletion or renaming to authorized owners.
Purpose and use
On a shared directory, the sticky bit restricts removal or renaming of entries by users.
How does it work?
Even when several users can write to the directory, rules consider file ownership, directory ownership and privileges.
Example and verification
Check this bit when a temporary directory must accept multiple users without ordinary cross-user deletion.
Points to watch
It does not encrypt files or by itself protect their contents against reading or modification.
In short
The sticky bit limits selected directory-entry operations rather than every form of data access.