The first world war was fought in the trenches of Belgium and France and in parts of the world like Gallipoli. Artillery and ships were used amongst other weapons.
WW2 was more widespread geographically. All parts of Europe were involved spreading into Russia, North Africa and the Middle East, and an extensive Asian front in India, South-East Asia, and Japan where the US played a major role. The opponents were organized in and fought as national armies, navies and air forces, controlled by governments.
Today’s terrorist attacks, especially over the past 15 years, have taken place in different parts of the globe, conducted by non-traditional forces often located among civilian populations. When these terrorists are attacked by regular military personnel, civilians are placed in danger or forced to move from their traditional homelands. The result is flows of refugees who live in squalid camps or undertake dangerous passages to what they perceive to be safe havens in places like Western Europe and North America.
Since 1914, there have now been three world wars, the last one currently being fought in the Middle East and parts of the world where terrorist acts can be undertaken either by local inhabitants or by persons who can easily cross borders. Modern societies have many places where bombings can occur to kill people, disrupt lives and capital equipment – power grids, travel (road, rail, air, ships), commercial activities dependent on communication systems, cyber attacks on computer networks and so on.
For most of the post WW2 period, potential threats have focused on nuclear attacks from countries with this capability. Today’s threats can be undertaken with equipment like drones, individuals willing to perish as suicide bombers, and other low cost measures which are impossible or hard for civilized societies to guard against.
A listing of terrorist attacks by year and location can be found at https://en.wikipedia.org/wiki/List_of_(non-state)_terrorist_incidents
They have occurred in all parts of the world including major incidents like 9/11, bombings and shootings in Madrid, London and Paris, as well as many in other locations. Travelling the globe today is a bit like travel by horse and coach in earlier days when highway men could be expected to attack and there was no protective police force. Today, I would argue, we are in the midst of WW3 with techniques used which are far different from those used in WW1 and WW2.