Bombs may seem impossible to make but actually they are simple to make and many people could make them just from taking a chemistry class in high school. Terrorist do not use a specialized bomb. They are mostly hand crafted bomb with a different aspect to its make up. Even though bombs can be easily made, people who do not have the skill of a professional bomb disposer should not try to dismantle the bomb. There are different ways to fuse a bomb, but most bombs have basic elements.
Bombs have three fundamental things in common.
Each of these elements must be contained in the bomb for it to work. All bombs are set off by a detonator which is a steel tube around two inches wide and about one fourth on an inch deep. The detonator has to set off the explosive charge to make an explosion. This is an interesting topic, and a great start. I can clearly tell that you had to do some research on this topic.