Book excerpt: Studying Jihadism is an endeavor facing several problems. For many researchers and the reading public it is difficult to accept that Jihadists do have a theology of their own and not some kind of ideology. Understanding that a phenomenon of communication that is done to a large extent in Arabic is not to be understood if research is done communication translated into or written in English. Saying it is al out there in the Internet without understanding Internet communication will help to understand terrorist phenomena like Jihadism. Ignoring that there is Jihadism IS and al-Qa'ida will guarantee that research will not be able to see the broad range of Jihadism. Last but not least, research not interested in the technologies, practices, etc., Jihadists use to commit terrorist attacks, cannot claim to study Jihadism. The contributions in this book provide knowledge in all these fields: based on Arabic language sources, theological aspects, Internet communication, groups usually ignored, the role of infographics, technical aspects, and covert and intelligence actions.