A dream journal is like a special book where you write down your dreams just like you might write a story. Every night when you go to sleep, your brain creates lots of pictures and ideas that make up your dreams. Sometimes those dreams are silly or scary, and other times they're like a big adventure!
By writing down your dreams in a journal, you can remember them better and think about their meanings. Maybe you keep having the same dream over and over and can't figure out why - writing it down can help you understand it better. Plus, it's fun to read your dream journal later on and remember all the cool things your brain created while you were sleeping!