ePUB (sometimes written ePub) is an electronic book format. It is named as a shortened version of 'electronic publication'. It was made an official standard of the International Digital Publishing Forum in 2007, and is in mainstream use in several popular ebook marketplaces. Apple's iBooks and store use ePub as a standard format, although there are Apple-designed supersets of ePub available for more complex layouts. Barnes & Noble's Nook, the Kobo and various other devices use or can use ePub. The notable holdout is the 800-lb gorilla in the marketplace, Amazon, whose Kindle line of e-readers use .mobi or .azw format ebooks. An argument can be made that .mobi, at least, is mostly just a lightly warmed over and proprietary version of ePub, but those are questions for lawyers and pundits.
ePUB version 3 (EPUB3), standardized in 2014, has additional features to support more precise or customized layout and formatting, which makes it more usable for publications such as illustrated volumes and comic books; it also supports MathML. ePUB's official format can be found on the IDPF website for the most up to date technical specifications.
Generally, ePUB can handle the following list of features or data, which is by no means complete.
- DRM - There are provisions for a DRM layer, but the ePUB spec itself does not contain or specify one.
- HTML - Most text content in an ePUB is in HTML format.
- CSS - Layout is generally done via CSS files, in a dedicated 'Format' subdirectory
- Images - At least JPEG and SVG formats, and perhaps others
- Fonts - Font files in OpenType or TrueType format can be embedded within an ePUB for consistent rendering
Many popular word processors and specialized writing software packages will spit out ePUBs with a little effort. Scrivener is one such which does what I consider the least-horrible job - the code it puts out is at least legible.
Once you have an eBook in ePUB format, it is easily converted to Amazon Kindle format or any other using either Amazon's own tools, or an eBook manager such as Calibre.