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.
The question you're asking is designed to solicit opinions or best-practices on a particular topic, with the goal of reaching community consensus.
when you have an idea for a new feature, or a change to the existing functionality.
What's on topic and what's not. How should we define or change our scope as we find topics that are currently off topic but shouldn't be, and vice versa.
for discussions about tag synonyms, e.g. which existing pairs of tags should be merged, which not yet existing tags should be created as synonyms, policies regarding synonyms.
Questions about the site's design
Questions about the reputation users earn from having posts upvoted and performing helfpful tasks, which as they accumulate will unlock privileges on the site.