Well, essentially it’s an extension of the Apple iCloud service, it allows you to upload and store all of your music in the Apple cloud and have access to it anywhere…. at a price.
Here’s what Apple has to say about it:
iTunes Match stores your music library in iCloud and allows you you enjoy your collection from anywhere, anytime, on your iPhone, iPad, iPod Touch, Computer or Apple TV.
Millions of Songs to Match
Any of your songs already in the iTunes Store are automatically available in iCloud.
Listen at 256 Kbps DRM-Free
Play matched songs in iTunes Store quality. Even if your original was of lower quality.
With iTunes Match, even songs you’ve imported from CDs can be stored in iCloud. And you can play them on any iPhone, iPad, iPod touch, Mac, or PC — whenever you want and wherever you are, without syncing. iTunes Match is just $24.99 a year.
It’s more than just centralized storage though. Let’s say that you ripped a CD to your computer – Apple will check the music from the CD to the available tuned in the Apple iTunes store and makes those tracks available to you for download at better than ripped quality.
At an annual cost of $24.99 per year it’s not terribly cheap – and compared to Amazon’s Cloud services, which is free to Amazon purchases, its really quite expensive.
Of course, there are limits. You can use 10 devices with iTunes Match (I’m up to 4 devices) and 25,000 songs (yeah, I’m nowhere near that).
Here’s how it works: iTunes determines which songs in your collection are available in the iTunes Store. Any music with a match is automatically added to iCloud for you to listen to anytime, on any device. Since there are more than 20 million songs in the iTunes Store, chances are, your music is already in iCloud. And for the few songs that aren’t, iTunes has to upload only what it can’t match. Which is much faster than starting from scratch. Once your music is in iCloud, you can stream and store it to any of your devices. Even better, all the music iTunes matches plays back from iCloud at 256-Kbps AAC DRM-free quality — even if your original copy was of lower quality.Limits? 10 devices and 25,000 songs [Apple]