Not for generic relationships! Use this tag only for questions involving a significant other or sexual partner.
Often people will have a significant other whom they really "click" with, and they often want to spend the rest of their lives with them. However from time to time, issues can appear in any relationship, and so questions with this tag often refer to issues relating to someone's significant other.
Should also be used with location tags such as united-kingdom, however should not be used for tags such as friends. For committed, long-term partnerships, the life-partner tag may also be used.