The ePub format is based on XHTML - it's a kind of website with CSS and more. Because the text is reflowable you don't have separate pages as such, and the positioning of images is limited. Producing proper ePubs needs to be learnt as it's not at all intuitive.
For an overall survey of the subject you might have a look at the recently published book "ePublishing with InDesign CS6: Designing and producing digital publications for tablets, ereaders, smartphones, and more" by Pariah Burke
Also the online Lynda.com course: http://www.lynda.com/EPUB-tutorials/InDesign-CS6-EPUB-Kindle-iPad/98834-2.html. I believe you can have a month's membership free. You can then subsequently ask specific questions on this forum as there are some very knowledgable members on here!
Ok so I have finally found an answer to my specific question after hours and hours of searching.
I could not understand why the default document setup for Ipad in CS6 gave me a page that is way bigger than the Ipad resolution;
In the Document Setup when creating my epub, I chose 'Digital Publishing' as my Intent. Now that I have changed it to 'Web' (72 dpi)
the resulting document is much closer to the Ipad screen size.
thank goodness I can now move on from that confusing issue.