There were three Gorgons in the usual classical family of sisters: Medusa, Stheno, and Euryale. The word Gorgon therefore refers to a group of three figures, not only to Medusa.
The three sisters appear in ancient Greek mythology as daughters of the sea deities Phorcys and Ceto. Medusa was mortal, while Stheno and Euryale were immortal. This difference is central to the Perseus story, because Perseus could kill Medusa but had to escape her surviving sisters.
Modern retellings sometimes use “Gorgon” as if it were Medusa’s personal name. That usage reflects Medusa’s fame, but the original mythological category included all three sisters. Ancient art and literature also varied in how prominently each sister appeared, with Medusa becoming by far the best-known figure.