The FictionBook 2.0 file format was developed in Russia and gained popularity there. Whereas other eBook formats contain multiple XML files an FB2 file contains just one. The format is DRM free and is open source. As the name suggests, FB2 files often contain fiction eBooks, however this is not a technical restriction. The format was designed to enable the file to be converted to other file types relatively easily.
The FB2 file contains a tagged structure that allows software applications to interpret and render the content accordingly. This means that elements such as quotations and subtitles can be defined, in addition to formatting such as bold, italic or underline. Typically, an FB2 file contains the Stylesheet, Description and Body. All text to be displayed is contained within the Body section which uses a nested structure to allow subsections and paragraphs to be defined.
The LRF file type is a proprietary file type created by Sony for use with Sony branded eBook readers. LRF, along with LRS and LRX made up the now defunct BroadBand eBook or BBeB. The file type was discontinued in 2010 with the Sony eBook store selling in the ePUB format.