Multi-Touch book is Apple’s name for ebooks made with its iBooks Author ebook building software. Multi-Touch books can contain a number of advanced features—such as embedded videos, picture galleries, 3D models, pop-up sidebars, interactive slideshows, and more—and they can have elaborately designed layouts.
However, unlike EPUB, a format with a well-defined open standard, the Multi-Touch format is owned by Apple. As a result, Multi-Touch books can be read in iBooks on the iPad and on the Mac—and on nothing else. (That shouldn’t be a problem for you; if you didn’t have iBooks, you probably wouldn’t be reading this book!)
Multi-Touch books were originally seen as the digital textbooks of the future, as this article