Similar page results

Is anybody can tell me how google show similar pages link below the main search results.

Going by my own site’s pages, the “similar pages” are canonical. That is, if I have something like:
mysite/archive/SEO-success.php
mysite/topic/SEO-success.php
mysite/topic/SEO-success.php?sort=1
mysite/whatever/SEO-success.php

then Google shows one of those links in the results and the others if I click the similar pages link.