In practice, explosive are employed to fill certain roles. The nature of the role determines which mode of explosion, ie burning or detonation, is required. The explosive will then be caused to function under conditions regulated to ensure that it behaves in the desired manner. Explosives can therefore be classified under the role in which they are normally employed. Explosive which normally function in burning mode are sometimes called "low explosives". However this term is now discouraged because such compositions are mostly propellants of various kinds, they are nowadays called "propellant explosives" or simply "Propellants"

We can include in our scheme of functions the class of materials known as pyrotechnics/fireworks although they do not share all the characteristics of explosives which are set out in this site. Pyrotechnics are mixtures of oxidising and reducing solids, capable of self-sustained combustion at rates which differ greatly from one composition to another. They are designed to produce special effects which supplement those produced by conventional explosives, and are outlined below:

1. HIGH EXPLOSIVES detonate to:
Create shock waves
Burst/Shatter
Penetrate
Lift and heave
Create air blast
Create underwater pulses

2. PROPELLANTS burn to:
Propel projectiles and rockets
Start I.C engines and pressurise
other piston devices
Rotate turbines and gyroscopes

3. PYROTECHNICS burn to
Ignite propellants
Produce delays
Produce heat/smoke, light
and/ or noise

Another way of classifying explosive is by the readiness with which they are ignited and exploded, that is, their sensitiveness to initiation. Substances which are readily ignited or detonated by a small mechanical or electrical stimulus are called PRIMARY explosives; those which are not readily initiated thus, and therefore require the influence of an impinging shock wave to initiate them, are called SECONDARY explosives. (propellants are not normally initiated by either of these methods in practice, but by the application of flame.)

A primary high explosive can be detonated easily.

A secondary high explosive can be detonated, but less easily.

A propellant explosive is not required to detonate at all.