An eBook is an electronic book, simple enough right. This is a book you read digitally on your computer, laptop screen, cell phone, PDA or on devices called ebook readers.
So why buy an ebook?
Well they're a lot cheaper than regular books.Usually between a $1.99 and $7.00. They take up less space, instead of book cases full of novels, you can have a file on your PC. You can also search for your favorite authors on line and download them almost instantly.
The most popular formats for ebooks-
HTML
ADOBE PDF - Adobe Acrobat
LIT - MS Reader
PRC - MobiPocket, Kindle
For more reading on ebooks & their formats-
http://en.wikipedia.org/wiki/E-book
http://en.wikipedia.org/wiki/Comparison_of_e-book_formats
To download reader software for your computer-