A .38 Special is not, as I thought, a type of pistol. Rather, it is a type of cartridge. A cartridge is what we mistakenly think of as a bullet; in fact, it's the package of bullet, jacket, and primer.
According to the Wikipedia:
...it is a rimmed, centerfire cartridge designed by Smith & Wesson. It is most commonly used in revolvers, although semi-automatic pistols and some carbines also use this round. The .38 Special was the standard service cartridge of most police departments in the United States from the 1920s to the 1980s. In other parts of the world, particularly Europe, it is known by its metric designation 9x29mmR.
Its caliber is actually .357-.358 inches in diameter. It gets its name from the diameter of its loaded brass case.
The .38 Special traces its history to the Philippine-American War. Its predecessor, the .38 Long Colt, the standard military cartridge, was found to have inadequate stopping power; hence, the development of the .38 Special.
To date, it is the most widely produced firearm cartridge in the world.