Energy swords were a form of Goa'uld melee weapon. While they looked just like regular swords, they were able to be "switched on", which made the sword glow with some form of energy, allowing it to cut through objects easier. These weapons were first encountered by the Tau'ri on a planet guarded by Serpent Guards along with a vo'carr chronicling Mars's defeat by Ares.
SG-1 later encountered the same type of weapons on Kar'tek, where Mars's cyborg Jaffa wielded them along with staff weapons. After being capture by these Jaffa, Teal'c was given one such energy sword to fight in the colliseum. He used it to defeat both the Minotaur and Medusa before he was defeated in combat by the Hydra.
Behind the scenes
Energy swords were never actually given a name in the Stargate SG-1: Fall of Rome 1 comics, but have been given the conjectural title of "energy sword" for the purpose of this article.