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.
For questions concerning area51 proposals.
Systematic biases in the Academia.SE site and community, e.g. in answering questions in an idealized vs. realistic way.
Regarding the predefined and custom close reasons shown to users in the "vote to close" interface. (Use [closed-questions] instead if asking about a question that has been closed.)
On the community comprising users of Academia.SE, its demographics, etc.
a flag that can be applied to answers (and questions) which lowers the barrier for editing and prevents any rep gain/loss from voting.
For questions about the removal of comments--could refer to when or why a comment is to be removed.
About removing content from Academia or Academia meta.
Questions about web and graphic design of Academia Stack Exchange.
about elections to choose moderators for the site, which happens once each year.