ePub stands for e-Publishing. It has been adopted as the international standard for publishing e-books. Once you have published your e-book you can then give your student access to the document or you can publish it via your itunes. If it is something that others may use or enjoy you can even distribute or sell it via ibooks.
http://appsineducation.blogspot.com/2011/05/epub-publishing-your-own-ibooks-for.html