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 answer the question owner thought best met their needs. This tag is for discussing issues related to accepted answers, not indicating that a question has an accepted answer.
when examining what is on-topic or off-topic, and why.
for questions specifically about the process of asking questions on a Stack Exchange site.
For questions about fostering a sense of community among users of the site
a flag that can be applied to answers (and sometimes questions) which lowers the barrier for editing and prevents any rep gain/loss from voting.
The Stack Exchange Data Explorer (SEDE) allows you to create and run queries against copies of the databases of popular Stack Exchange sites.
"Design" refers to front-end elements, such as page layout, coloring conventions, etc.
for questions or issues surrounding login to this site.