Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In a support group, members provide each other with various types of help, usually nonprofessional and nonmaterial, for a particular shared, usually burdensome, characteristic. The help may take the form of providing and evaluating relevant information, relating personal experiences, listening to and accepting others'' experiences, providing sympathetic understanding and establishing social networks. A support group may also work to inform the public or engage in advocacy. Formal support groups may appear to be a modern phenomenon, but they supplement traditional fraternal organizations such as Freemasonry in some respects, and may build on certain supportive functions (formerly) carried out in (extended) families. Other types of groups formed to support causes, including causes outside of themselves, are more often called advocacy groups, interest groups, lobby groups, pressure groups or promotional groups. Trade unions and many environmental groups, for example, are interest groups. The term support group in this article refers to peer-to-peer support.