Kindle/Mobi is the proprietary format used for Amazon Kindle eBooks, which can be read on the Amazon Kindle hardware eBook readers and a wide variety of Kindle apps on different platofrms. Internally, this format is really just a minor variant of the universal ePUB format. However, Kindle eBooks are packaged in a proprietary Amazon binary format instead of in a normal ZIP file like standard ePUB. There are just a few formatting and configuration changes that need to be made and these are handled automatically by Help+Manual.
The ePUB format (file extension .epub) is a standard for eBooks created by the International Digital Publishing Forum. It is the standard eBook format on Apple iOS devices, which currently include the iPad, the iPhone and the iPod Touch. Help+Manual's ePUB output is designed to be fully compatible with the Apple iBooks® eBook reader on these devices so that you can distribute your ePUB output through the Apple iTunes store.
In addition to Apple iBooks®, ePUB is also supported by most other hardware eBook readers, including the Sony Reader series, other smartphones and many other devices, and by many software readers like the Adobe Digital Editions reader.
See ePUB Resources for more details, including sources for reader software and devices.
Please note that the support for ePUB and Kindle eBooks only included in the Professional and Server versions of Help+Manual. You cannot generate these eBooks with the Basic version.