A social networking service is an online service that focuses on building and reflecting of social networks or social relations among people. A social networking service essentially consists of three things. First, a representation of each user. Second, his or her social links. And third, a variety of additional services. Most social networking services are Web-based. They provide means for users to interact over the Internet, such as email and instant messaging. Online community services are sometimes considered as a social networking service in a broader sense. However, a social networking 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 ones containing category places, means to connect with friends and a recommendation system linked to trust. Many networks focus on providing both services and community to individuals with shared interests.