With the release of iOS 5 and OSX 10.7.2, the two operating systems have bonded like never before with iCloud. But what exactly is it, and what does it do?

iCloud is Apple’s replacement to MobileMe. Through iCloud, you’ll use your Apple I.D. to sync data between your iOS 5 device and your Mac running 10.7.2 and iTunes 10.5 (or Windows XP or higher machine). Without all three of these, iCloud won’t work to the full extent. You’ll also be able to see your data on icloud.com. So what’s going to be synced? Well you’ll have the option to choose between all of these, some of these though will only be Mac specific, but we’ll get to that in a minute. You get 5 gigabytes of iCloud storage for free, though you can pay to go up to as much as 50. Paying also gives you iTunes Match, allowing iTunes to scan and match up to 25,000 songs you have in iTunes and stream that from the cloud.

Universal:

• Apps: When you download apps, they’ll automatically be synced through iCloud to your Mac. When iTunes opens up, all the apps you’ve downloaded will be synced to it through the web. App data will also be synced, meaning that your 3 stars in Angry Birds will also be stored.
• Photos: With iOS 5’s Photo Stream enabled, you can have photos taken on your iDevice or from your computer streamed and synced from the cloud. These are synced across all your iCloud enabled devices. Not every picture you take is automatically sent to the cloud, only if you enable Photo Stream. 1000 are stored at any given time in iCloud.
• Music: Through iCloud, all your iTunes music is available for download on all your devices. Any music your purchase on one device can be automatically synced, or you can selectively choose what songs sync to what device. You can also redownload past purchases you’ve made through iTunes onto your devices. For iTunes Match, where you can stream your songs from the cloud, will be $24.99 a year.
• Books: Any books you’ve downloaded through iBooks will be synced through iCloud and available on all your devices, as well as any book marks and the last place you were in a particular book.
• Contacts and Calendar: Contacts and calendars on iOS 5 will be synced through iCloud, available on the website, and synced to your main computer. On Mac these will be synced to Address Book and iCal respectively, while on Windows it will sync to Microsoft Outlook.
• Mail: Signing up through your Apple I.D., you get a free @me.com. It will be synced through Apple’s Mail & iOS’s Mail App. You’ll also be able to check it on the iCloud website. That is also free, though it counts toward your storage.
• Find my iPhone: Available since iPhone 4, Find My iPhone has moved to iCloud.com. You can still use another iOS 4 or higher device to track your missing device, but now iCloud is the web home of tracking your iDevice
• Notes, Reminders: Notes and Reminders from your iDevice will also be synced through iCloud, You won’t be able to see them outside of your iDevice, but they will sync across your iDevices.
• Backup: iCloud lets you back your iPhone into your iCloud account, just like it does when you plug your iDevice into your Mac and run the sync feature in iTunes. Next time you get a new iDevice running iOS 5 or later, all your stuff will be downloaded onto that new device through the Wifi.

While iCloud is still new and the real test will come in the near future as more people use it, iCloud still seems like a worthy and logical upgrade for all iOS users.