LurkerFAQS is an archive of the GameFAQS message boards. Because there are thousands of boards on GameFAQS, only a selected few are archived.
Please visit here for a complete list of boards
You can search for a GameFAQs user and view their archived posts.
You are able to view archived topics even after they're purged on the original boards.
Let's say someone sends you a link to a topic:
You go to the topic, but find out it has been purged. If the topic is on a board archived by LurkerFAQs, you can simply replace gamefaqs with lurkerfaqs in the URL to find an archived version of the topic.