When Bilbo finds the dwarves, he discovers that the dwarves have been captured by the goblins.
While Bilbo was playing a riddle game with Gollum for a magic ring, Gandalf and the dwarves were in some trouble of their own. They were fending off goblins in the caves. They were just arguing about what to do about Bilbo when came up upon them. Gandalf was pleased to see him, glad he was proven right about his burglar’s mettle.
The wizard, to tell the truth, never minded explaining his cleverness more than once, so now he had told Bilbo that both he and Elrond had been well aware of the presence of evil goblins in that part of the mountains. (Ch. 6)
The fact that the dwarves had their own adventure while Bilbo had his shows that there is danger in many parts of Middle Earth. It also demonstrates that Gandalf knows more than he is telling, and may be testing Bilbo. This is an important chapter too because it gives Bilbo an opportunity to explain his riddle game and how he escaped Gollum, and the presence of the ring. The truth he tells, or does not tell, is significant to Gandalf. He alone knows the meaning of the One Ring.
Bilbo’s separation from Gandalf and the others is part of his development as a hero. The hero’s journey involves separation from the group, and trials and tests along the way. Bilbo’s test in the belly of the beast shows that he is strong, and clever. He overcame Gollum, returned, and brought with him a useful treasure in the ring. He used that ring a few times after that to help the company get out of some tight spots. Despite Gandalf’s reservations about it’s possible evil, the right had its purposes.
After Bilbo found the ring and won the riddle game with Gollum, he made his way out of the cave and reunited with the dwarves. He discovered that the dwarves were in a it of a mix up with goblins. He then helps the dwarves and Gandalf get away.
Bilbo finds the dwarves and Gandalf, who killed the Great Goblin and many others when he helped the group escape.