AZW3 - Kindle Format 8 (KF8) is Amazon's newer version of AZW. It supports HTML5 and CSS3 which were not supported through the standard AZW format. It has a number of other formatting options and is used by Amazon for all new Amazon eBooks. It is supported by fourth-generation Kindle devices running firmware version 4.1.0 or later and the Kindle Fire device.
KF8 (also called AZW3) is essentially a compiled ePub that has utlises a Palm database and Amazon's DRM scheme. It targets ePub 3 version support but existing ePub can also be used. The internal format has been decoded using mobi_unpack. The basic format remains as a PDB file similar in structure to a MOBI. More oftent than not a KF8 file will contain both a MOBI file at the beginning and the newer KF8 version of ePub later.
Associated programs
Kindle Fire Kindle Reader Kindle for Android Kindle for iOS
The .rb file format was created by NuvoMedia to read eBooks on their Rocket eBook device. Released in 1998. The device could hold approximately 10 books and is no longer manufacturered. Several online bookstores sold .rb eBooks.