Explosives
The generic name of 'explosive' is applied to all explosive substances. Those for which deflagration (see below) is the normal process of combustion or breakdown are called gunpowder.

Explosives are classified in three major groups: propellants, blasting explosives and initiators. Propellants are gunpowder-based and are used to shoot bullets from guns, for example, or to propel rockets. Blasting explosives and initiators, on the other hand, can be chemical or compound explosives.

Explosive substance
Refers to all types of chemicals or compounds whose combustion or breakdown initiates an abrupt release of energy.

Combustion 
A phenomenon whereby an explosive substance, such as petrol, combines with the oxygen in the air as a combustive agent, thus giving off heat and a release of gases.

Combustive agent
This is the name for a substance that, when it combines with another substance, causes its combustion. Oxygen is a combustive agent, but is not combustible.

Deflagration
A phenomenon of intramolecular combustion (within each molecule) or intermolecular combustion (between two or more molecules from different kinds of chemical systems), without oxygen from the air or any other external combustive agent taking part in the process. It burns quickly with flames and without an explosion.

Detonation
Phenomenon of intermolecular or intramolecular combustion propagated by means of a shockwave moving at high speed, independent of pressure.

Implosion
Refers to the process when a structure collapses inwardly. An implosion is the complete opposite of an explosion, and occurs when the external atmospheric pressure is greater than the internal pressure.