With around 300 million active users worldwide, Facebook is the largest social online network. More than one billion chat messages are exchanged daily, over 100 million search queries are made, and up to 600,000 photos are viewed every second. In Germany, Facebook has also become the most popular social network, with nearly nine million monthly visitors and an estimated six million active users. In the future, the operators plan to enhance its appeal further with downloadable songs and a global mood barometer. However, even now, more and more advertisers are taking notice of this popular platform. This book provides an overview of the social network Facebook, who is behind it, and why it is so successful.