Terrorism is a threat, a modus operandi and a phenomenon. A resolution of the UN General Assembly after 9/11 designated it as a threat to international peace and security. As an MO, from a largely uni-dimensional threat of the years before the Arab-Israeli war of 1967, it has evolved into a multi-dimensional threat. As a phenomenon, it has many dimensions-political, economic, ideological and operational. Even the profile of a terrorist keeps changing. The terrorists of yesterday were seen as \"misled youth\" from the exploited or wronged sections of society. An increasing number of the terrorists of today are educated and come from well-to-do families. They are self-motivated and technology savvy. Their ability to add sophistication to their methods of operation surpasses the skill of the security agencies. This book seeks to contribute to the task of understanding terrorism as it is evolving. Its author, B.Raman, headed the counter-terrorism division of the Research & Analysis Wing (R&AW), India's external intelligence agency, for six years and has continued studying the subject even after his retirement in 1994. He is well known as an analyst of terrorism in India and abroad. He is much in demand in international conferences on terrorism. His prolific writings on this subject are widely read and his views are heard with attention and respect.