For a firearm to operate, there must be an energy source to impart kinetic energy to the projectile being fired. This is is true in general, but our discussion shall be limited to small arms with only a couple of exceptions. These materials are called propellants, and the name is quite apt.
The first propellant used was blackpowder, the exact origin of which is lost in antiquity. For centuries, actually up to very late in the 19th century, blackpowder was the only propellant available.
In the late 1880s what is now called smokeless powder was developed, and has replaced blackpowder in almost all applications except for what I refer to as “boutique” ones. A substitute for blackpowder, Pyrodex(R) was developed , along with some other substitutes for reasons that will become apparent later.