I know this is starting really basic, but just for those who are wondering.
An ebooks is an electronic version of a book, often of a book that exist first as a printed book. Ebooks can be read on a computer or handheld device designed specifically for this purpose, provided the computer or device has the necessary software for the format of ebook being used. Sometimes people use the term “ebook” to refer to a dedicated device used for reading electronic versions of books.