An ebook is an electronic (or digital) version of a book. The term is used ambiguously to refer to either an individual work in a digital format, or a hardware device used to read books in digital format. Some users deprecate the second meaning in favour of the more precise "ebook device."

In most cases the ebook is delivered via download, and in most cases comes in .pdf format which is the industry standard for digital books and documents. In order to read the ebooks, you will need to down Adobe Reader, whch is 100% free. Most computers these days already come equipped with the tool, so you may already own it. If not, you can get you'ew own copy by following this link. 

 http://www.adobe.com/products/acrobat/readstep2.html

Other books may come in the Windows.EXE format which simply requires you to be running Microsfot Windows on your computer.

In addtion, some Windows ebooks actually require you to be connected to the internet to read, because they are simply live web pages that are placed into a portable format and accessible to anyone who has internet access.