1.1 Introduction Terrorism is a highly complex, highly subjective and politically sensitive topic. In this chapter we will address some of this complexity, subjectivity and sensitivity. We will show why and how terrorism is receiving much attention from both the media and governments and how it impacts on societies. Discussing the geographical distribution of attacks and casualties we will arrive at what can be called the defi nition problem of terrorism. We will explore the questions about what can be labelled terrorism and what not, and why it is actually important (and diffi cult) to defi ne the term. Finally, we discuss the nature of terrorism: what it is about, what it does it to society, and how it works. Th at terrorism indeed has an impact on society we can read in the papers and see on television and on the internet. In fact, terrorism is making headlines almost every day and almost everywhere around the globe. In recent years, major attacks or series of attacks hav...