The terrorism was not born in a vacuum is silly. Reason being is the individuals who oft use it apply it to only the west. Using it to condemn the west and say they are getting what they deserve. Experience shows these are usually also the same people that argue slavery is uniquely the sin of the west and more so the US. Like we invented it. Never mind that Joseph was sold into slavery as evidence how long that wrong has been going on.
Same with terrorism you can open the old testament and see it in operation. One example is Samson taking the foxes tying the torches to their tails then setting them to burn down the fields.
Terrorism is in simple terms unconventional warfare striking at the weakest link to force or pressure or bring about a objective or goal.
Citizens are the weakest link and more so today than in history because today a good portion of citizens have the power of the vote. So the means employed can be as you said and strike at the most vulnerable. Or can even be as
@ZNP has given of cell groups attacking infrastructure.
Since you can't beat a nation or force change through conventional means of the military. You use other means to strike fear or terror into the citizens eroding their confidence in their own government to protect them, feed them, and etc. Attaining your goal or objective by the citizenry calling for government to change course.
However, it has been around as long as mankind has sharpened sticks or placed a stone in a sling.