The site's FAQ is important but intentionally terse; Meta is better for fleshing out supporting arguments and finer points, but it's a pain to find.
The faq tag is meant to help make sort of a long-form FAQ on Meta, one we could link to (linking to the tag actually, or a question compiling FAQ entries).
Should we start compiling some FAQ questions on Meta? Do we have any existing posts that would be useful? Are there trip-ups common enough for this to be useful?
For the record, if you see a Meta post that's important enough to be an faq question, go ahead and flag it and explain that. The faq tag can only be added by moderators.