When you count all the different ways Windows 10 will be available, there are actually seven different editions: Windows 10 Home, Pro, Enterprise, Education, Mobile and Mobile Enterprise, plus several versions designed for Internet of Things devices and embedded systems.
The list of SKUs makes most sense when you divide it up by screen size, because that is what controls the user interface you see, as well as the features you get. Windows 10 Mobile and Windows 10 Mobile Enterprise are for smartphones and tablets that have screens smaller than 8-inch; they have the Windows Phone-style screen, the Edge browser without Internet Explorer, and come with the Office for Windows 10 apps pre-installed.
Windows 10 Home, Pro, Enteprise and Education are for desktop PCs, laptops, 2-in-1s, convertibles and larger tablets. Mostly, they're the equivalent of the similarly named Windows 7 and Windows 8.1 editions. In this article, we'll go through the exact details of each version…
Windows 10 Home
The version of Windows 10 that you're most likely to get if you buy a new PC, Windows 10 Home, has the key features of Windows 10, from the new Start menu to the Edge browser, to the Windows Hello biometric login feature that uses your face or fingerprint instead of a password, to Cortana – the voice-controlled assistant from Windows Phone.
Windows 10 Home includes game streaming from Xbox One, which lets you play games from your Xbox One on your PC instead. To keep home users more secure, updates come from Windows Update, and you don't get the option not to install critical and security updates.
Windows 10 Home includes the Continuum feature for tablets. This is the tablet mode that simplifies the taskbar and the Start menu, and makes your apps full screen – you can split your screen between two apps, but this is much simpler than the way Windows 8.1 let you arrange windows on-screen.
If you have the Home version of Windows 7 or 8.1, Windows 10 Home is what the free upgrade will get you.
Windows 10 Pro
If you use your PC for business, Windows 10 Pro has extra features over Windows 10 Home – the most important of which is being able to join a domain, including Azure Active Directory for single sign-on to cloud services (and have group policy applied as part of that).
You also get Hyper-V for virtualisation, BitLocker whole disk encryption, enterprise mode Internet Explorer, Remote Desktop, a version of the Windows Store for your own business, Enterprise Data Protection containers (a feature that comes later in the year) and assigned access (which locks a PC to running only one modern application, to use like a kiosk). Pro users can get updates from Windows Update for Business, which includes options for scheduling updates so they don't reboot PCs at important business times.
There are ways of connecting Windows Home PCs to a server, but if you want the familiar business PC experience, Windows 10 Pro is what you need. It will be a free upgrade from the Pro versions of Windows 7 and 8.1 (which includes Windows 7 Ultimate as well as Professional, and Windows 8.1 Pro and Pro for Students), you'll be able to upgrade to it from Windows 10 Home, and some desktops and notebooks designed for business will come with Windows 10 Pro.
Windows 10 Enterprise
Windows 10 Enterprise has all the business features of Pro, and adds a number of more powerful features designed for larger companies: Direct Access for connecting without a VPN, AppLocker for whitelisting apps, BranchCache for sharing downloads and updates with other PCs using a peer-to-peer connection, and group policy for controlling the Start Screen.
There's also Credential Guard and Device Guard features for protecting Windows logon credentials and locking down which applications a PC can run, and the option of keeping a PC on the Long Term Servicing Branch where it gets only security updates (ideal for systems you need to have working reliably for years without being affected by new and changing Windows features).
The free Windows 10 upgrade doesn't apply to Windows Enterprise; that's because you can only get it with a volume licence (and you have to already have a Windows Pro licence for each PC), and if you have a volume licence you already have the option of Software Assurance, which includes upgrades.
Windows 10 Education
Windows 10 Education is a new SKU, designed for large academic organisations like universities that want the security, management and connectivity features of Windows 10 Enterprise (it's common for students to need to join the domain to use official printers, for example).
The feature list is almost identical to Windows 10 Enterprise but it doesn't have the Long Term Servicing Branch and instead of having to upgrade from Windows Pro, you can upgrade directly to Windows 10 Education from Windows 10 Home. That means educational establishments can easily make Windows 10 Education available to students bringing in their own PCs.
Windows 10 Mobile
If you use Windows Phone or a small (8-inch or smaller) tablet with Windows 8.1, when you upgrade what you get is Windows 10 Mobile (a confusing name, given that Windows Mobile was the smartphone OS that Windows Phone replaced). It's also what will come on new devices. The idea is that a 5-inch or 6-inch phone and a 7-inch tablet aren't really very different devices, so having the same interface and – crucially – the same universal apps on both makes more sense (and gives Microsoft a better chance of getting apps for its platform).
Windows Mobile has the key parts of Windows 10, including the Edge browser and the new touch-friendly version of Office – but it doesn't include IE. If you have the right hardware, you'll be able to plug your phone or tablet into a display and get the Continuum interface, with a bigger Start menu and the same interface you'd see for universal apps on a PC.
Windows 10 Mobile Enterprise
The version of Windows Mobile for larger businesses who have volume licences includes similar tools for managing updates to Windows 10 Enterprise, although we don't know if they're exactly the same as Windows Update for Business and the Long Term Servicing branch.
Windows 10 IoT
If you have a Raspberry Pi 2 or an Intel Galileo or a range of other 'maker boards' you can get a free version of Windows 10 for them that can run universal apps. There are also Industry and Mobile versions of Windows 10 that OEMs can put on more traditional embedded devices like point of sale systems, cash tills, ATMs and other machinery.
The Industry version is for x86 systems only and it can run a wide range of software; the Mobile version is for tablets and handhelds that might have x86 or ARM CPUs and they can run universal apps. This is the embedded version of Windows Mobile – it's for the kind of device you might use for entertainment on a plane or for checking stock in a warehouse.