Azw files are electronic books in the so-called Amazon Kindle eBook format. This format is the native Ebook format of the Amzon Kindle and can only be read with these devices or the Amazon Kindle readers for Windows, Mac OSX and various mobile platforms such as the iPhone.
The Amazon Kindle is a reader (ebook reader) for electronic books, magazines and other publications. Commercial AZW files can only be purchased on Amazon and must be transferred to the Kindle for mobile reading.
The AZW format is in principle a version of the Mobipocket (prc) ebook format extended by some DRM functions. Under certain circumstances, unprotected AZW files can also be read with the Mobipocket Reader by simply renaming the extension AZW to prc.
To create AZW files yourself, there is Amazon KindleGen. Among other things, this command line program can be used to convert html and epub files into the AZW format. Alternatively, you can also create a Mobipocket book (prc, mobi) with the MobiPocket Creator or Reader, for example, and change the file extension to AZW. The Kindle recognizes this book as a DRM-free AZW book.
Amazon now also uses the endings azw1 and tpz for its ebook files, which both represent an extended format and are not directly compatible with AZW.