The famous English poet John Milton once wrote ‘The mind is its own place, it can make heaven of hell and hell of heaven’. The term ‘Terrorism’ has recently been defined by Paul J. Smith, a security expert at the Asia-  Pacific Center for Security Studies, as a form of psychological warfare that is used to create extensive fear through the use of extensive force against non-combatant civilian military targets. It thrives in a milieu characterised by some festering and unresolved issue in an atmosphere of financial crisis and in situation where unlawful trade in narcotics and small arms. The possibility of proliferation of Weapons of Mass Destruction (WMD) through the innovation of modern technology is more real today than it has ever been in human history. Weapons of Mass Destruction terrorism involves the most modern and the most extreme form of random violence. Nuclear, chemical and biological weapons are inherently terrifying; in most cases of their being used, the fear they would cause would dwarf the injury and death. Its dreadful nature creates its own dangers; of victims panic and try to flee, they spread contamination and disease still further. The effects of these weapons are also inherently random. The radius of injury depends on conditions that are impossible to control or predict with certainty. The use of these innovations for terrorist activities is limited only by the imagination of the terrorist. Every one is a potential target and this creates a climate of fear and suspicion within a society.
Terrorism defined by scholars and groups
Different scholars have tried to come to terms with terrorism depending upon their ideological moorings. Today terrorism is the new form of warfare then it is evident that politics for some states has become an offshoot of this deadly virus and has acquired its own autonomy.  For example, Yonah Alexander, links terrorism with national security. To him, ‘terrorism is the use or threat of violence against random or civilian threats in order to intimidate or create generalised pervasive fear for the purpose of achieving political goals’. But Paul Wilkinson makes a difference between political terrorism and other forms of violence. He defined political violence as “the systematic use of murder and destruction, and the threat of murder and destruction in order to terrorise individuals, groups, communities or governments into conceding to the terrorists’ political demands”. While the United States’ Department of State defined it as a, “pre-meditated, politically motivated violence penetrated against non-combatant targets by sub-national groups or clandestine State Agents, usually intended to influence an audience.” In the state of terrorism, nation found itself in a condition in which it is very difficult to provide security and the environment of development to its citizens in terrorist affected areas. In so many cases terrorists also run their parallel government in specific part of territory, in this situation governments face so many challenges for safeguarding territorial integrity and preserving sovereignty of the nation state.
On the other hand, terrorism has been analysed by several social science disciplines, intelligence agencies, militaries, law enforcement agencies, IGOs and NGOs and legislatives and judicial bodies. They all use different type of framework, institutional perspectives, requirements and dimensions. According to them terrorism seems to possess four key elements – I. cause (generally political), II. non-state entities with group dynamics, III. chosen place and IV. indiscriminate use of violence. When all these four key elements combine together they create an environment of psychological fear and terror, all these combined are known as terrorism.
Different forms of terrorism
In a nutshell, despite lack of consensus on what terrorism actually encompasses, there are, however, certain features common to all forms of terrorism. For instance, terrorism, in all forms, is aimed to generate fear, panic and terror in the minds of the general public. It may be politically motivated or may emerge because of obscure ideologies or beliefs, the acts of terror may be perpetrated for political ends or for changing the cultural norms or religious ethos of a targeted country or a segment of population. Further, terrorism, unlike ordinary violence, employs inordinate lethal force against civilian targets to erode the political will of the targeted country, undermine the morale of the people, spread despondency and panic through catastrophic terrorist attacks. Moreover, terrorism is arbitrary and unpredictable as far as its effects are concerned. And it does not recognise any rules and conventions of war and geographical limitations.
Who is a terrorist?
Thus, a ‘terrorist’ is a person who indulges in criminal acts with manifestly political motive without exhausting legitimate remedies at his disposal for the redressal of his grievances. His acts may be organised or unorganised, sporadic or widespread, commanding public support or hatred. The decisive element is that he indulges in criminal acts without invoking legitimate remedies for his alleged grievance or suffering. The terrorist hypothesis is that the system itself suicides in response to the multiple challenges of death and suicide. Neither the system, nor power, themselves escape symbolic obligation and in this trap resides the only chance of their demise (catastrophe). In this vertiginous cycle of the impossible exchange of death, the terrorist death is an infinitesimal point that provokes a gigantic aspiration, void and convection. Around this minute point, the whole system of the real and power gains in density, freezes, compresses, and sinks in its own super – efficacy. The tactics of terrorism are to provoke an excess of reality and to make the system collapse under the weight of this excess. It indicates that terrorist actions are both the magnifying mirror of the system’s violence and the model of a symbolic violence that it cannot access. By using violence and terror, terrorists disturb communal harmony in society, create fear and suspicion between communities. That is why they pose and direct threat to maintaining domestic peace.
In its latest manifestations, terrorism is violence for a cause and terrorists always want the world to know about their existence, their causes and the power they wield.  From the ongoing discussions the theories of terrorism have been derived as 01.Terrorists are not born but created by particular sociological, economic and political conditioning  processes,02.Terrorism is not based on reason and is nothing but a series of senseless and mindless actions to create fear, 03. It is deliberate and systematic assault on civilians to inspire fear for political ends, 04. It is a method whereby an organised group or party seeks to achieve its avowed aims, chiefly through the systematic use of violence, 05.It is a weapon of the weak employed against powerful opponent not with the aim to defeat but as an attempt to show itself as all powerful and a good force with a view to change the balance of power.
To conclude terrorism is not an act, but, it is a thinking in which some people think that political objectives could be achieved by illegitimate use of violence. Its motivations are also changing. A new breeds of terrorist including ad hoc groups motivated by religious convictions or revenge, right-wing extremists and apocalyptic and millenarian cults, appear more likely than terrorist of the past to commit acts of extreme violence. Religious groups are becoming more common and are more violent than secular groups.