The "BFG," or "Big Friendly Giant," is a children's book written by Roald Dahl. It tells the story of a young girl named Sophie who befriends a gentle giant. Unlike other giants, the BFG is kind and loves to collect dreams, which he shares with children while they sleep. In the story, the BFG and Sophie work together to stop the other giants, who are not friendly and eat humans. The book explores themes of friendship, bravery, and the importance of standing up against bullies. It has been adapted into various formats, including a popular animated film.