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.
MP3 is a digital music format which allows CD tracks to be reduced to around a tenth of their normal size without a significant loss of quality. MP3 gets rid of a lot of the information recorded in a song that our ears are not able to hear and then uses complex algorithms to reduce the file size. This then enables you to get hundreds of songs on to a CD and it also has opened up a new market over the internet - the download market as download times have been significantly reduced.
The MP3 format is a lossy format. That means that an MP3 file does not contain 100% of the original audio information. Instead, MP3 files use perceptual coding. In other words, that means it removes the information that your ear doesn't notice thereby making the file smaller. The reason lossy formats are used over RAW is that RAW audio files are too large to travel over the internet at any great speed. By using lossy formats it enables even dial up users to download mp3 files at a reasonable speed. RAW file formats generally require 176,000 bytes per second compared to a lossy format which requires 17,600. The difference is massive and so are the download times.