Treebeard and his people are called Ents in J.R.R. Tolkien’s legendarium.
Ents are tree-like shepherds created to protect the trees of Middle-earth. Treebeard, whose Sindarin name is Fangorn, is one of the oldest living beings in the story and lives in the forest that also bears his name.
In The Lord of the Rings, the Ents hold the Entmoot and decide to attack Isengard after learning about Saruman’s destruction of forests. Their assault overwhelms the fortress and helps end Saruman’s power. The Ents’ slow decision-making contrasts with the urgency of the War of the Ring, but their strength is immense once they act.
Ents are not the same as Huorns, a related and more mysterious tree-like group. They are also distinct from the Maiar, the angelic order that includes Gandalf and Saruman. Treebeard’s people are best understood as sentient guardians of trees.