The template implements the class unconfirmed-show, which displays its content only to readers who are unconfirmed (IP users and new users).
It takes the text to be shown/hidden as its first unnamed parameter and encloses it in a span (i.e. inline). Adding anything as a second parameter (suggested "block") will cause the text to be displayed as a block element.
Usage
Inline
Some text.{{Unconfirmed only|This is only seen by unconfirmed readers.}} More text → Some text.This is only seen by unconfirmed readers. More text
Block
Some text.{{Unconfirmed only|This is only seen by unconfirmed readers.|block}} More text → Some text.
