Windows Phone 10 or Windows 10 Mobile?
Actually, it's neither although Microsoft does refer to it as Windows 10 Mobile in terms of the Insider Preview builds. For the first time we'll see full Windows 10 running on phones. Yep, you'll get exactly the same operating system on your phone, tablet, laptop or PC.
Microsoft will tailor its OS to devices 8in and above, however, with a slightly different version for Windows phones and small screen tablets. We'll talk more about this below. Also see: Best Windows Phones 2015.
Windows 10 for phones: UK release date and supported phones
Windows 10 is now available on phones because Microsoft has launched the Lumia 950, Lumia 950 XL and Lumia 550. These all come with the new operating system pre-installed out-of-the-box.
That's a good start but what about those of you who already have a Windows Phone handset and simply want the software upgrade to Windows 10?
The good news is that Microsoft is starting to roll out updates starting December.
"Windows 10 is available on PCs and tablets now, and while Lumia 950 and Lumia 950 XL ship with Windows 10 for phones, broad availability of Windows 10 on other devices, including mobile phones, will begin rolling out in December." said the firm.
You'll need to be updated to the Lumia Denim version of Windows Phone in order to get the software upgrade to Windows 10. Certain devices will get it first with Microsoft describing the following phones as 'a first list of Lumia smartphones that will receive a free upgrade when available'.
"Lumia 430, Lumia 435, Lumia 532, Lumia 535, Lumia 540, Lumia 635 (1 GB RAM), Lumia 640, Lumia 640 XL, Lumia 735, Lumia 830, and Lumia 930. Features may vary by device. 8 GB of internal memory required."
There's more good news as Microsoft has made good on its promise to take control of the firmware updates, no longer leaving up to networks to sort things out. This should make the process much quick with some networks holding back new releases for many months.
"Microsoft is working closely with mobile operators to leverage their testing and our flighting to meet and exceed current quality bars. We will use their input but will decide when to send the updates out based on input from mobile operators and our Windows Insiders," said the firm.
Insider Technical Preview
If you can't wait any longer, the Technical Preview is available and you can install it by following the link to our guide at the top of the page. At first the Technical Preview was only available for a handful of phones but a 'partition stitching' feature will allowed many more phones to get the software.
Here is the official list of supported phones which can use the Windows 10 Technical Preview:
HTC One (M8) for Windows, Lumia 430, Lumia 435, Lumia 520, Lumia 521, Lumia 525, Lumia 526, Lumia 530, Lumia 532, Lumia 535, Lumia 540, Lumia 620, Lumia 625, Lumia 630, Lumia 635, Lumia 636, Lumia 638, Lumia 640, Lumia 640 XL, Lumia 720, Lumia 730, Lumia 735, Lumia 810, Lumia 820, Lumia 822, Lumia 830, Lumia 920, Lumia 925, Lumia 928, Lumia 930, Lumia 1020, Lumia 1320, Lumia 1520, Lumia Icon.
You can also join with the Lumia 950, Lumia 950 and Lumia 950 XL if you want to get the latest updates.
Unfortunately, not all Lumia phones will get Windows 10.
Windows 10 for devices with smaller than 8in screens: New features
Joe Belfiore showed a very early build of Windows 10 for devices with 8in screens or smaller at its 21 January Windows 10 event. The OS was seen running on a Lumia 1520. It will roll out to Insiders in February.
He said the Start experience is quite familiar for users running Windows Phone in the past, and will be a great companion to the PC. In the background is a full-bleed background image, and when you swipe in from the right to reveal the app tray you find recently installed apps at the top of the list.
The Action Centre has some new features and is now synched with the PC. You can expand action buttons and dismiss single items shown as notifications.
Settings, as seen on the desktop, has also been streamlined and implemented as a universal app, removing the confusion of having both a Control Panel and Settings menu.
Belfiore also demonstrated how Microsoft wants to evolve input and messaging. The Word Flow keyboard has been improved, letting you pull it over to the right and doing shape writing with one hand, and you can use voice input to reply to messages by clicking the microphone button. The speech system is sophisticated enough to recognise names, hashtags and insert punctuation.
It has also built-in support for IP-based messaging services and Skype.
Universal apps will work with phones, small tablets and PCs, delivering everything you need for productivity. A family of apps will be built into all Windows 10 devices, bringing continuity as you move from device to device. Belfiore showed a preview version of Office on the phone, and said full Word, Excel and PowerPoint will be included on phones - complete with Office Ribbon. A recent documents list will be available to all Windows 10 devices.
Continnum works in conjunction with Universal Apps and phones such as the Lumia 950 can we used on a larger screen providing a 'PC-like' experience. This can be done wirelessly or with the Microsoft Display Dock. You get a proper desktop and can use a mouse and a keyboard while using the phone itself like normal.
With hardware acceleration you'll be able to give proper presentations from your phone.
New versions of Outlook Mail and Outlook Calendar will also be found on phones, tablets and PCs. The full Word engine will be built into the email app. Swipe gestures let you flag or delete messages.
Photos also work exactly the same way as they do on the desktop, with both phone and PC using exactly the same code. It will automatically enhance photos and remove duplicates.
Project Spartan is the new web browser Microsoft is developing for Windows 10. It will come to the phone eventually, but won't be in the first builds.
Spartan has a new rendering engine that's compatible with today's web. It has a new look and feel, and it has three significant features that will make you more productive on the web, according to Belfiore.
First is the ability to mark up articles on the web with comments before you share them, either through touch or with a keyboard. Second, Spartan improves reading on the web. Its reading mode supports PDFs and can be personalised, and includes a reading list that shows up on all your Windows 10 devices. This content is then available to read offline. Lastly, Spartan brings Cortana to the browser, and can help you find the information you need faster.
Windows 10 for phones: UK price
For the first year Windows 10 will be a free upgrade for all devices running Windows Phone 8.1. Thereafter Microsoft pledges to keep your smartphone up to date and secure for the lifetime of the device, viewing Windows 10 as a service rather than a software update.
Microsoft quotes via ZDnet.
Follow Marie Brewis on Twitter.