What are they?

Explosives and energetic materials comprise of substances that are unstable and can produce a sudden expansion of material, usually accompanied by the production of heat, pressure, a flash, smoke and noise.

Some energetic materials are extremely shock-sensitive and can explode with very little energy applied to them in the form of heat, shock, friction or a chemical reaction. Conversely, some substances are stable and are only capable of exploding via ignition from other more energetic materials.