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 about the entire network of Q&A sites that make up the Stack Exchange network.
Questions about sizes and other quantities of Stack Exchange sites, e.g. number of questions, GB/day transferred, etc.
Users without full edit privileges can suggest edits to posts and tag wikis.
For questions about real world stackexchange / code-review branded items.
A request to add one tag as the synonym of another tag. Please be specific about which tag should be a synonym of which. Bidirectional synonyms and cycles are implicitly disallowed, so suggest wisely.
For questions about the syntax highlighting performed inside code blocks on Stack Exchange sites.
keywords or labels that categorize and group your question with other, similar questions.
for questions about tag synonyms (how they work, who can create them, etc). Use [synonym-request] for tag synonym requests.
an editable page that briefly summarizes the topic of the tag and that may provide links to existing questions that are often useful to many people.
for questions referring to a non-Stack Exchange controlled entity.
A programming tool or software development tool is a computer program that software developers use to create, debug, maintain, or otherwise support other programs and applications.
about the top 7 question list on the Stack Exchange blog.
For questions about internet trolls and trolling on Stack Exchange sites.
Tweeting the "interesting" and "hot" things to Twitter via the integration of bots.
those questions which have no up-voted answers.
for questions specific to upvotes, the community's way of telling peers that their content was clear and helpful. Up-votes on the meta sites may have different meanings.
Refers to user accounts either generically, or across the network.
The user interface elements and web pages that make up this site.
User retention refers to keeping a user who has come to our site, coming back again and again.