iBooks Author: placeholder
Each template contains text and media placeholders, which you can replace with your own content.
Placeholder text shows you what text will look like and where it will appear in a book. After you replace the text with your own (just click the placeholder text and type), you can change the formatting if you like.
Media placeholders are locations in a template where you can drag your own media (images, movies, and more). When you drag an item to a placeholder, you don’t have to delete the current item first; just drag a new item to the placeholder and the old item is replaced. When you drag your own files to these placeholders, your media is automatically sized, positioned, and framed to fit the template, but you can modify your media as you can other objects.
To see whether an item is a placeholder, let the pointer rest over it; if it’s a placeholder, a help tag appears.