Do you know the difference between a fact and an opinion? It can be a hard thing to understand. Some things are facts--like the number of robots in this book. Other things are opinions--like which robot would make the best friend, or which robot dances best. And sometimes to tell the difference between a fact and an opinion, you need to wait to get more information--that's because facts can be proven true or false, and opinions are things you feel and believe--but that you can't prove.