Summary: what all links were supposed to be, but for various reasons weren't.
link link at the bottom of each answer produces a permanent link to that answer. Regardless of whether the answer is moved to a different question, or voted onto a different page (for questions with many answers), or both the question and answer are edited so heavily that they no longer bear any resemblance to their original form, that link will always take you to it. At least, until the answer is deleted.
Ok, so it's a *semi-*perma-link... They all are, really.
Point is, you can click it, and copy the URL out of your address bar, and spread it around freely, confident in the knowledge that it won't stop working just because the question rolled off the front page or got re-titled.