The traillink directive is supplied by the
trail
plugin. It generates a visible WikiLink, and also adds the
linked page to the trail represented by the page containing the directive.
In its simplest form, the first parameter is like the content of a WikiLink:
[[!traillink some_other_page]]
The displayed text can also be overridden, either with a | symbol or with
a text parameter:
[[!traillink Click_here_to_start_the_trail|some_other_page]]
[[!traillink some_other_page text="Click here to start the trail"]]