Microsoft’s upcoming Windows 8 operating system arrives this week. If you haven’t been paying close attention, the operating system’s new interface might come as a shock.

Microsoft has designed Windows 8 to work with many computing devices, with the exception of smartphones. You can use it on desktops, laptops, tablets, and hybrids like Samsung’s Smart PCs. Windows 8 runs on many older PCs and will come installed on all kinds of cool new devices.

Here are eight things you need to know about Windows 8.

1. When does it come out?

You can download Windows 8 from Microsoft’s website on Friday, Oct. 26. If you prefer, on the same day you can purchase it in physical form at retailers such as Best Buy, Staples, Office Depot, the Microsoft Store, and Amazon.com.

2. How much does it cost?

For the vast majority of people running Windows today (XP, Vista, or 7), Windows 8 Pro costs $40 to download and upgrade using the Windows 8 Upgrade Assistant. Online upgrades are available in 140 countries and 37 languages. Microsoft says this offer expires on Jan. 31.

If you purchased a new non-Windows 8 PC after June 2 and before Jan. 31, you’re eligible to upgrade to Windows 8 Pro for just $15. Frankly, that’s a hell of a deal, as long as you like the new interface.

3. What are the differences between Windows 8, Windows 8 Pro, and Windows RT?

As with most Microsoft operating systems, Windows 8 comes in several different versions.

Windows 8 is the most basic version of the operating system, specifically targeting consumers. It includes most everything you would expect to have, including the Start screen; major apps like Mail, Music, Calendar, and Internet Explorer 10; the Windows Store, and the desktop. Pricing and availability for plain Windows 8, weirdly enough, has not been announced.

Windows 8 Pro, as far as we can tell, is the only version of Windows 8 available to consumers on launch day. It includes everything in plain Win 8 and more. Unlike plain Windows 8, it also includes features that power users might want like BitLocker, client hyper-V, domain join, encrypting file system, support for group policy, and remote desktop hosting. (These features are pretty advanced and mostly fulfill the needs of businesses and the overly paranoid.)

Windows RT shares a large amount of code with Windows 8 and looks a lot like it, but it is designed for different kinds of machines. It only runs on ARM-based processors that are more commonly found among smartphones and tablets rather than the x86 processors usually used in desktops and notebooks. Most notably, RT does not allow you to use software designed for x86/64 and legacy desktop software. It only works with software from the Windows Store. (In that, it’s much like Apple’s App Store with iOS.) RT also includes a reworked, less-powerful version of Office with apps for Word, Excel, PowerPoint, and OneNote. RT does not include Windows Media Player. The first time we’ll be able to fully test Windows RT is on the initial version of the Microsoft Surface tablet.