azw3 The American company Amazon is a recognized powerhouse when it comes to all things related to books. Their proprietary eBook readers dubbed the Kindle which was first released in 2007 is a testament to this. The .azw file format is the filename extension associated with eBooks designed to be read on Amazon's proprietary Kindle device and through their free but closed source Kindle software for smartphones, PCs, and Macs. The format is incompatible with any device other than kindle and its associated software. In order to open files saved in this format on non-kindle devices, one would have to convert the file to another format such as the open ePub format or PDF. Some converters can also convert other formats into .azw files which can later be opened on a kindle device or application.
lrf The LRF format is a proprietary format developed by Sony in collaboration with Canon, as a document and text encoding standard for the Broad Band eBook file format. The format specifically targeted Sony portable eBook readers and was capable of encoding both text, pagination, and images. Being unencrypted, LRF encoded files do not enforce DRM. This is in contrast to the LRX format which is also part of the BBeB eBook file format which does support encryption for DRM files. The Sony eBook store announced in July 2010 a discontinuation of support for the LRF format in favor of the public and open EPUB format.