Tells you what the book or chapter will be about
Title
Table of Contents
Tells us what page to find specific information or chapters

Table of Contents
How do headings help the reader?
They tell what the section is about.
Tells us they are words to know and that they are very important
Bold Words
Gives us a snapshot of what the book is telling us
Picture
Where is the caption?

'Polar bears in the world'
What is the heading of this page?

What is a shark?
Show us WHERE things are
Map
Describes Pictures
Captions
What is this?

Map
How do the labels help us understand the diagram? 
Gives us the definition of bold words
Glossary
Tells us what each specific section will be about
Heading
Where can you find definitions of important words?
Glossary
How to photographs help the reader?
They show exactly what an object looks like.
Explains parts of a diagram
Labels
Tells us where to find certain words
Index
What is this book about?
How do you know?
What animals build...
Because architects build things.
How do captions help a reader?
It explains what is happening in a photograph.