A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.
Questions about how to promote Unix & Linux Stack Exchange, in order to attract more users.
Public Service Announcement
for asking for guidance to help reopening a closed question or requesting a question to be re-opened after a revision.
For questions about reputation, a measurement of a user's contributions to the site, and the extent to which the community "trusts" that user with extra privileges
Use when the question is about when it is appropriate to add or remove tags while editing a question.
Use for questions that discuss the proper way of reviewing items in the review queue, or the review queue mechanism itself.
when examining what is on-topic or off-topic, and why (i.e scope of the site).
Indicates that a change in functionality is currently under consideration, or needs further investigation.