what is accepted on our site and what not, how to deal with X

According to Wikipedia,

A policy is a deliberate system of principles to guide decisions and achieve rational outcomes. A policy is a statement of intent, and is implemented as a procedure or protocol.

So this tag shall be used whenever a question is about …

  • Is X a valid question/answer?
  • Do we deal with Y as topic?
  • Do we permit Z in questions/answers?

And only for this kind of Meta-question. Using a dedicated tag for this makes it easier to find relevant details, so please make use of it :)

Also see: scope