A print book is one that can be held in your hands. It is a physical book made of paper and cardstock or cardboard such as those on the library shelves.
Electronic books, or eBooks, are digital versions of books that are meant to be read completely online. Examples of ebooks include books from EBSCOhost, Overdrive, Safari, Netlibrary, Google Books, Open Library.
Place your mouse over the orange tab above that says Citing Books. You'll see specific examples of both types.
To get more information, use one of the print manuals or one of the online guides on the Introduction page, or ask a librarian for help.