In Tolkien’s fiction, what kind of creature is Smaug?

In Tolkien’s fiction, Smaug is a dragon.

Smaug is the principal antagonist of The Hobbit. He occupies Erebor, the Lonely Mountain, after driving out the dwarves who once ruled there. His hoard includes the enormous treasure of the Kingdom under the Mountain, and his possession of it motivates the company’s expedition led by Thorin Oakenshield.

Smaug is portrayed as intelligent, eloquent, proud, and highly dangerous rather than as a simple animal. Bilbo Baggins meets him inside the mountain and uses riddling conversation to learn about his nature. During that encounter, Bilbo notices a vulnerable area in Smaug’s armor-like hide.

The dragon’s story concludes when Bard the Bowman uses the information about that weakness to kill him with the Black Arrow. Smaug is not the same kind of being as a Balrog, which is a different creature associated with Tolkien’s mythology and The Lord of the Rings.