iTunes, which comes with Mac OS X Snow Leopard, is a media player that plays audio and video files. These files can be in any of many different formats. Some of the more common file formats that iTunes supports are
MP3: The small size of MP3 files has made them popular for file trading on the Internet. You can reduce MP3 files to a ridiculously small size (at the expense of audio fidelity), but a typical CD-quality, three-minute pop song in MP3 format has a size of 3 to 5MB.
AAC: Advanced Audio Coding is very similar to MP3; in fact, AAC files offer better recording quality at the same file sizes. However, this format originally supported a built-in copy protection scheme that prevented AAC music from being widely distributed on Macs. (Luckily, this copy protection is no longer applied to iTunes tracks, and you can still burn protected AAC tracks to an audio CD, just as you can MP3 tracks.) The tracks that you download from the iTunes Store are in AAC format.
Apple Lossless: This Apple format provides the best compromise between file size and sound quality: These tracks are encoded without loss of quality. However, Apple Lossless tracks are somewhat larger than AAC, so it’s generally the favorite of the most discerning audiophile for his or her entire music library.
AIFF: The standard Macintosh audio format produces sound of the absolute highest quality. This high quality, however, also means that the files are pretty doggone huge. A typical pop song in AIFF format has a size of 30 to 50MB.
WAV: Microsoft created its own audio file format (WAV) that works much like AIFF. It can reproduce sound at higher quality than MP3, but the files are very large.
CD audio: iTunes can play audio CDs. Because you don’t usually store CD audio anywhere but on an audio CD, file size is no big whoop.
Movies and video: You can buy and download full-length movies, TV shows, music videos, and movie trailers from the iTunes Store. And, with an Apple TV unit connected to your home theater system, you can watch those movies and videos from the comfort of your sofa on the other side of your house.
Podcasts: These audio downloads are like radio programs for your iPod, but iTunes can play and organize them, too. Some podcasts also include video and photos to boot.
Ringtones: iPhone owners, rejoice! iTunes automatically offers to create ringtones for your iPhone from the tracks you’ve bought from the iTunes Store.
Audiobooks: No longer do you need cassettes or audio CDs to enjoy your spoken books. iTunes can play them for you, or you can send them to your iPod for listening on the go.
Streaming Internet radio: You can listen to a continuous broadcast of songs from one of tens of thousands of Internet radio stations, with quality levels ranging from what you’d expect from FM radio to the full quality of an audio CD. You can’t save the music in iTunes, but it’s still great fun.
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Source:http://www.dummies.com/how-to/content/different-types-of-video-and-audio-that-you-can-pl.navId-323204.html
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