1.Beorn is a man who lives beyond the Misty Mountains. He’s a huge fellow, very strong, and he can transform into the shape of the bear. Beorn is a little prickly and not too fond of strangers, but he absolutely, totally hates goblins. Thanks to his the-enemy-of-my-enemy-is-my-friend logic, Beorn provides Gandalf, Bilbo, Thorin, and the other dwarves with a place to stay after they escape from the Misty Mountains.
2.Gandalf knew Beorn would never accept so many visitors at once. By telling their story, he gained his interest and respect, and by introducing the dwarves a few at a time throughout the story, he gained Beorn’s acceptance of the whole group.