Children sometimes make assumptions about the world that keep them from understanding new information. They might not realize that plants and trees are alive because they don't move like humans and animals do or that their teachers live at school.
This is why it can be helpful to find out what children already know—or what they think they know—before introducing new material. You'll be able to correct the wrong assumptions (but not before writing them down in their baby books). With the correct information in place, they can continue to build on their knowledge of the topic.