They walk home, best friends.

Meaning: This means that the dog and the stranger are walking to the place where they live and they have a strong liking for each other.

Choice of Words: Home means the place where someone lives. Best friends means people who are very close and have a strong liking for each other. When you put them together, "They walk home, best friends" means that the dog and the stranger are walking to the place where they live and they have a strong liking for each other.