Tolkien calls the giant tree-like beings in The Lord of the Rings Ents. The Ents are ancient shepherds of trees who live in Fangorn Forest and are led by Treebeard, one of the oldest beings in Middle-earth.
Their name comes from an Old English word meaning giant or supernatural being. Tolkien encountered the word in Anglo-Saxon literature, especially the phrase eald enta geweorc, usually translated as the work of ancient giants. He transformed that linguistic source into a distinctive people within his mythology.
The Ents become important when Merry and Pippin reach Fangorn Forest after escaping from the Uruk-hai. Their gathering, called an Entmoot, leads them to decide to attack Isengard, the stronghold controlled by Saruman.
Ents are sometimes confused with Huorns, related tree-like beings that are less fully described and more mysterious. Treebeard is an Ent, not a Huorn, and the Ents’ march against Isengard is one of the story’s major turning points.