This is an interesting one. Suppose you're <<display>>ing a passage using the shorthand, and you include some extra values at the end of the tag:
<<CaramelCanoe "oars" "satchel">>
With parameter(), you can access these extra values and use them inside the displayed passage:
::CaramelCanoe You're canoeing down the caramel river, rowing with <<print parameter(0)>>, your <<print parameter(1)>> by your side.
Running the aforementioned «display» will show “You're canoeing down the caramel river, rowing with oars, your satchel by your side.”
This allows you to subtly alter a passage depending on where and how it's «display»ed, without using variables. You can, for instance, make a passage that describes the character's clothes, and you can supply different adjectives to the passage, just by including them in the shorthand «display».