A social networking service is an online service, platform, or site that focuses on facilitating the building of social networks or social relations among people who, for example, share interests, activities, backgrounds, or real-life connections. Its service 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. Online community services are sometimes considered as a social network service, though 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. Like Facebook, twitter and their role in the Egyptian revolution.
We will start by introducing Facebook one of the most important social networks all over the world. Facebook is a social networking website launched in February 2004, operated and privately owned by Facebook Inc. May 2012. It reached more than 900 million users; more than half of them using cell phones, iPod, iPhones & tablets Users cannot access the site unless you register, after having a Facebook account, add and search for new friends, and send messages, including notifications when they update their profile. Moreover, users may join common-interest user groups, organized by workplace, school or college, or other characteristics, and categorize their friends into lists such as "People from Work" or "Close Friends". Good thing about Facebook is its privacy settings, the best for that matter. People can actually manage to control who sees their information and post like photos and comments and who doesn’t, or even who sees the profile at all.