An eBook is the digital media equivalent of a conventional printed book. eBooks can be read on your computer, PDA's, iTouch, many phones such as the iPhone and also on dedicated eBook reading devices called eReaders or eBook readers.
At this time, eBooks come in many different formats. You must be sure to purchase the correct eBook format for your eReader. At first it can be a little confusing, but soon you'll get the hang of it! It's just like when VCR's first came out and there were 2 formats: VHS and BETA.