All of these tags are replaced in the subject as in the message.

{[moodle. ???]} {[course. ???]} {[from. ???]} {[admin. ???]} {[to. ???]} {[event. ???]} {[usertarget. ???]}

This is replaced by the site data from the site. This data you filled in in Site Administration » Home Settings » Edit Settings

In place of ???you can put any of the columns of the course table (id = 1). The main ones being:

{[moodle.fullname]} - Replaces with full Site Name; {[moodle.shortname]} - Replaces with short Site Name; {[moodle.summary]} - Replaces with Site Summary; {[moodle.link]} - extra - Replaces with Moodle access link. Already in HTML format; {[moodle.wwwroot]} - extra - Replaces with Moodle access URL. It's the same as in Moodle's config.php.