Digital sound files must be organized and structured so that your media player can read them. It's just like being able to read and understand a different language. If the player "speaks" the language that the files are recorded in, it can reproduce the song and make beautiful music. If it can't speak the language, the numbers of the music don't add up, and you get an error message - and no music. Error messages are frustrating, but you have some defense against them if you understand the major audio file formats.
* WAV format is the most detailed and rich of the available formats in Windows XP. All the detail is recorded at the chosen bit rate and sampling speed, and it's all done without compression schemes. It's digital sound presented in all its glory. Unfortunately, it takes up huge amounts of memory in the process. Four or five minutes of WAV sound can consume 40-50MB of memory, making it difficult to store a decent number of files. For that reason, you seldom see these files being sold over the Internet - they're just too bulky.
* MP3 single-handedly powered the popularity of digital music. MP3 is an audio layer of the larger MPEG file format. Because of its small file size, MP3 files are ideal for listening on a computer or a portable player. The important thing to remember here is that this is a specific way to make the music file smaller while retaining much of the quality of the original CD or WAV file. Aside from size, the other advantage of MP3 is that it's almost universally recognized. It's the American Express of audio. Just about any media player or portable audio player can recognize and play an MP3 song. That makes it popular among users. It is not popular among most folks who sell music, however, because its small size lends to easy copying and distribution over the Internet.
* MIDI, or Musical Instrument Digital Interface, is radically different from any other format. Technically, MIDI is not even audio; it's a set of instructions on how something (like your computer's sound card) should create music. It's like a cookbook. The MIDI cookbook tells something that already has all the ingredients (the notes of the music) how to arrange them and play them to make music. Because it's just a set of instructions, the MIDI file size is quite small (often measured in kilobytes as opposed to the larger megabytes). How those instructions sound can vary depending on the device that is used to play those instructions. The sheet music for a Beethoven symphony makes no sound, but the music will likely sound better when played on a concert piano as opposed to a thrift-store keyboard. MIDI files are not often sold to the public as music, but MIDI does play a part in home recording.
http://tech.yahoo.com/gd/understanding-the-major-file-formats-wav-mp3-and-midi/153238;_ylt=AjLv
