The ring that Frodo Baggins carries in J.R.R. Tolkien’s The Lord of the Rings is the One Ring. Sauron forged it in the fires of Mount Doom to control the other Rings of Power and extend his domination over Middle-earth.
The One Ring can make its wearer invisible to ordinary sight, but its deeper importance is its connection to Sauron’s power and will. It is not harmless jewelry, and prolonged possession exposes characters to fear, temptation, and corruption. Frodo inherits it from Bilbo, who found it beneath the Misty Mountains.
The ring must be destroyed in the same volcanic fire where it was made. This creates the central mission of the novel: Frodo and Sam must reach Mount Doom while the Free Peoples fight Sauron’s armies elsewhere.
The Ring of Barahir and the Elven rings Narya, Nenya, and Vilya are separate objects. They are not alternative names for the One Ring.