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 usability of Stack Exchange sites and features on iOS devices. There are also tags (mobile-web) and (ios-app).
1 question
Created Jun 19 at 5:49
Tag watching (formerly known as favorite tags) allows a user to select a set of tags on a Stack Exchange site for highlighting in question lists.
2 questions
Created Jun 10 at 13:34