The following is a guideline to help you decide what age your story is most suited for, and to understand the standard number of manuscript pages used in each book genre. Traditionally, board books are short, non-fiction stories that show pictures of things in baby's lives. Picture books are generally for children 2-3 years old. They consist of large pictures and very few words, probably only a few hundred at most. These tend to be very simple stories, both fiction and non-fiction.
Pictures are often more important than the words.
Picture StoryBooks are what most people think of as traditional picture books. Of late, book publishers are buying manuscripts with fewer rather than more words. Stories are more complicated, and are usually read to children. Pictures and words have equal importance in these books. Easy Readers are intended to be read by kids, not to kids.