What is Microsoft Windows RT?
Characteristics and Limitations
Microsoft Windows RT is a variant of Windows 8 that runs only on tablets using a low-cost ARM-type processor, as opposed to the processors by Intel that have powered almost every other version of Windows since the beginning. Windows RT was introduced in late 2012, at the same time as Windows 8. Due to the many drawbacks of Windows RT, tablets running Windows RT are no longer in production.
A tablet running Windows RT cannot run conventional Windows applications written for previous versions of Windows. Windows RT can only run the new-style, full screen apps from the Microsoft Store. This means you can't install an alternate web browser, like Google Chrome or Firefox; you must use Microsoft Internet Explorer.
Windows RT devices came pre-installed with a specially engineered version of Microsoft Office, called Microsoft Office 2013 RT, that runs in desktop mode on Windows RT—that is, with regular, resizable, overlapping windows. You can also use the File Explorer and other basic Windows tools, on the Windows desktop of a Windows RT tablet. There is nothing else you can do in desktop mode, though, since everything else is to be run from the Start screen in full-screen mode.
Windows RT was not intended for business use. In addition to the limitations on what software it will run (and therefore what kinds of files you can open and share), the version of Microsoft Office that came with Windows RT is not licensed for business use, unless your company has a Microsoft Office volume license or subscription and you apply one of the company's device licenses to your tablet. Also, it does not include Microsoft Outlook (normally part of the Microsoft Office suite), meaning you have to use the scaled-down Mail app, or Outlook Web Access in Internet Explorer, to access a mailbox on a Microsoft Exchange or Office 365 system.
What Devices Came With Windows RT?
The original Microsoft Surface (produced 2012 to 2013), and its successor the Surface 2 (2013-2015), are ARM devices, and run Windows RT with Office 2013 RT. The original Surface Pro (2013) is based on Intel hardware; it runs the regular version of Windows 8.1 or Windows 10, and it supports all the same Windows desktop applications and functions on the Windows desktop as a regular computer (as well as new-style apps, of course). For the Surface Pro, Microsoft Office had to be purchased separately, and you could of course choose any edition or subscription you want.
Both looked the same at first glance:
All Surface models made after these are Intel-based devices running the regular version of Windows 8.1 or Windows 10, and Microsoft Office. Like the original Surface Pro, none of these come with Microsoft Office for free, with one exception: the Surface 3 offered a free one-year subscription through Office 365 Personal in 2015. All current models come only with a 30-day trial of Office 365, which anyone can sign up for anyway.
A few other manufacturers—Asus, Dell, Lenovo, and Samsung—made Windows RT tablets in 2012 and 2013, but then quit. Microsoft stopped producing the Surface 2 in early 2015, and thus ended the Windows RT era.
The Meaning of "RT"
The "RT" in Windows RT is like some other acronyms Microsoft has used in the past, in that they offer no official explanation for what it stands for. The underlying programming system for the new style of full-screen apps that run on Windows RT and Windows 8 tablets is called Windows Runtime, though. Since apps based on Windows Runtime are the only kind of software programs you can run on a Windows RT tablet, this is most probably the source of the name for this variant of Windows.
While Windows RT may be referred to fully with a version number (as in Windows RT 8 or Windows RT 8.1), that does not imply there are any regular Windows 8 features; if "RT" appears anywhere in the description of a device or its edition of Windows, then that means Windows RT.
Windows RT 10
In July 2015, Microsoft released Windows 10 (skipping version 9), for desktop computers, laptops, and Intel-based tablets. Windows 10 Mobile for ARM-based devices came out in late 2015, but this is based on Windows Phone; it only runs on mobile phones (not tablets), and has no desktop mode (as limited as that was in Windows RT). As for ARM-based tablets, Microsoft said in 2015 there will not be a Windows 10 RT.
In late 2015, though, Microsoft released an update to Windows RT 8.1 that added a Windows 10-style Start menu, but that's it. So far, no Cortana or Edge browser, or any of the other new features of Windows 10.
Then, significantly, in 2017, Microsoft announced Windows 10 S and Windows 10 on ARM, which both have some of the properties of Windows RT.
Given the significant limitations described above, Windows RT tablets, like Chromebook laptops, are more suited for individual users and students rather than business users. Since they are now out of production, this is only a concern if you are purchasing used equipment or items on clearance. If you are considering buying an older Microsoft Surface or similar Windows-based tablet, make sure to pick the right one for your needs.