According to Wikipedia: A social network service is an online service, platform, or site that focuses on building and reflecting of social networks or social relations among people, e.g., who share interests and/or activities. A social network service essentially consists of a representation of each user (often a profile), his/her social links, and a variety of additional services. Most social network services are web based and provide means for users to interact over the internet, such as e-mail and instant messaging. Although online community services are sometimes considered as a social network service. In a broader sense, social network service usually means an individual-centered service whereas online community services are group-centered. Social networking sites allow users to share ideas, activities, events, and interests within their individual networks.The main types of social networking services are those which contain category places (such as former school-year or classmates), means to connect with friends (usually with self-description pages) and a recommendation system linked to trust. Popular methods now combine many of these, with Facebook and Twitter widely used worldwide; MySpace and LinkedIn being the most widely used in North America; Nexopia (mostly in Canada); Bebo, Hi5, Hyves (mostly in The Netherlands), StudiVZ (mostly in Germany), iWiW (mostly in Hungary), Tuenti (mostly in Spain), Nasza-Klasa (mostly in Poland), Decayenne, Tagged, XING, Badoo and Skyrock in parts of Europe; Orkut and Hi5 in South America, India and Central America; and Friendster, Mixi, Multiply, Orkut, Wretch, renren and Cyworld in Asia and the Pacific Islands and Twitter, Orkut and Facebook in India.There have been attempts to standardize these services to avoid the need to duplicate entries of friends and interests (see the FOAF standard and the Open Source Initiative).Although some of the largest social networks were founded on the notion of digitizing real world connections, many networks focus on categories from books and music to non-profit business to motherhood as ways to provide both services and community to individuals with shared interests.