What is the inconspicuous contrast between terrorism, militancy, fundamentalism, insurgency?

Life does not become easy for an IAS officer when transferred to the disturbed areas of India; instead, it becomes much harder. Individual states like Jharkhand, Chhattisgarh, and North East are infested with Naxalites, and some states like Delhi, Jammu, and Kashmir, Ladakh, Mumbai are prone to terrorist attacks. Hence they are expecting a clear-cut answer. Terrorism is a condition where violence is used to put fear among the population to perform a political/religious/social objective. Militancy means the use of violence and aggression to support a political or social cause. Fundamentalism is to follow an ideology or religion or beliefs very strictly. Insurgency is more about rebellion against the authority or state.