Stormtroopers were the elite shock troops of the Galactic Empire, fanatically loyal and answerable directly to Emperor Palpatine.
Formed into the Stormtrooper Corps, stormtroopers operated alongside Army and Navy units, as well as alone.
It is possible that Palpatine had the Sith troopers of the ancient Sith Empire in mind, especially in the concept that the troopers induced fear as faceless enemies.
The stormtroopers were direct descendants of the clone troopers created from a template of Jango Fett in 32 BBY to serve the Galactic Republic's Clone Army during the Clone Wars. In fact, the clone troopers that lived after the end of the Clone Wars were renamed Imperial stormtroopers by Palpatine during the Declaration of a New Order; immediately afterwards, Palpatine ordered three new stormtrooper clone batches to be grown in the Outer Rim Territories.
During the time of the Galactic Civil War and the Battle of Yavin, Fett's clones were still used by the Empire, although Fett's progeny were heavily supplemented with clones from new DNA sources and troopers recruited in the traditional manner.