In human form, Beorn takes on the appearance of a tall, black-haired man with huge arms and a great black beard. He was capable of communicating with beasts. He was generally a benevolent individual who was both generous and helpful to those whom he was convinced were good; but he was distrustful of travelers and beggars, and hated both goblins and wargs.
Beorn provided Thorin Oakenshield and his Company of Dwarves (along with Bilbo and Gandalf) shelted and later helped them fight against an army of goblins at the Battle of Five Armies. During the battle, Beorn transformed into a giant bear and rescued Thorin from the Goblins and killed Bolg, the goblin chieftain. Following the battle, Beorn accompanied Gandalf and Bilbo along their return journey until they reached his house.
Beorn’s son, Grimbeorn, later took over his duties as chieftain (TA 3018). Beorn’s descendants were also skin-changers, known as Beornings, who helped defend Thranduil’s kingdom of northern Mirkwood.
Beorn is Old English for “warrior, a hero, man of valour”
It is also a cognate to the Old Norse björn (“bear”)