This template is used to explicitly notify people of the blocked status of a certain user. While everyone can add this tag, it should typically only be placed by the blocking administrator. If the blocker doesn't think it's needed, the odds are it isn't.
If the "ip" parameter is used and the "time=" parameter is not specified, then the page will be added to Category:Indefinitely blocked IP addresses.
The template adds the
__NOINDEX__ magic word.