The Ents appear in The Lord of the Rings as ancient shepherds of the forest and allies of the free peoples of Middle-earth during the War of the Ring. The Ent who figures most prominently in the book is Treebeard, who claims to be the oldest creature in Middle-earth. At the time The Lord of the Rings takes place, there are no young Ents (Entings) because the Entwives (female Ents) were lost.
A community of Ents once roamed the wastelands between Warrington and Runcorn. One of them can still be found, standing guard over a small plastic box. Don't wake him up!