Answer:
These lines mean that Bilbo has embarked on an unknown and completely unpredictable adventure. These lines suggest that Bilbo, contrary to what he imagined, was courageous and adventurous.
Explanation:
These lines were taken from the book "Hobbit," written by Tolkien, where we met Bilbo, a Hobbit, very kind, friendly and homely. In this book, we can see that Hobbits are very fragile and peaceful creatures in relation to other creatures in the same universe. This fragility, makes Hobbits feel safe only in the Hobbits community, because the world outside it is sinister, scary and dangerous. Bilbo shares this thought, but he, even with fear and insecurity, is very courageous and this can be seen when he decides to "leap in the dark" and face the world so frightening to embark on an adventure that would lead him to the treasure of Dragon Smaug.