The main idea of Chapter 7 is that the travelers stay at Beorn’s hut
After their ordeal with the wargs, the eagles drop them off and they take refuge at the home of a shapeshifter named Beorn. He can take the form of a bear or a man. He does not usually allow people to stay in his house, but he makes an exception for Gandalf’s company.
[He] has a great wooden house; and as a man he keeps cattle and horses which are nearly is marvellous as himself. They work for him and talk to him. He does not eat them; neither does he hunt or eat wild animals. (Ch. 7)
Gandalf explains that Beorn has his own magic. He is a friend to all of the animals. Beorn is suspicious of them at first, and checks out their story. Once he has verified it, he lets them stay there and gives them food for the journey. He also tells them how to get to the Lonely Mountain through Mirkwood.
Mirkwood is a dangerous place though. Beorn warns them to be careful. He tells them that it is difficult to find food and water, and the one stream that there is should be avoided.
There is one stream there, I know, black and strong which crosses the path. That you should neither drink of, nor bathe in; for I have heard that it carries enchantment and a great drowsiness and forgetfulness. (Ch. 7)
When they get to the edge of the forest, Gandalf says he is going on his way. Bilbo does not want Gandalf to go, but Gandalf leaves them with the advice to take care of themselves and stay on the path through Mirkwood.
This chapter is a turning point because Gandalf leaves again, and the dwarves and Bilbo are on their own through the forest. They do not know that Gandalf’s coming and going through the book are planned, and that he has important business to see to involving the dark magic of the Necromancer.