Windows 10 has several editions, all with varying feature sets, use cases, or intended devices. Certain editions are distributed only on devices directly from an original equipment manufacturer (OEM), while editions such as Enterprise and Education are only available through volume licensing channels. Microsoft also makes editions of Windows 10 available to device manufacturers for use on specific classes of devices, including IoT devices and previously marketed Windows 10 Mobile for smartphones.
Enterprise LTSC (Long-Term Servicing Channel) (formerly LTSB (Long-Term Servicing Branch)) is a long-term support variant of Windows 10 Enterprise released every 2 to 3 years. Each release is supported with security updates for either 5 or 10 years after its release, and intentionally receive no feature updates. Some features, including the Microsoft Store and bundled apps, are not included in this edition. This edition was first released as Windows 10 Enterprise LTSB (Long-Term Servicing Branch). There are currently 4 releases of LTSC: one in 2015 (version 1507), one in 2016 (version 1607), one in 2018 (labeled as 2019, version 1809), and one in 2021 (version 21H2).
Microsoft also warns that after the preview build of Windows 8.1 is installed, user won’t be able to use their PC recovery partition to go back to the previous version of Windows. You will have to use the original installation source, usually the DVD, to go back to the previous Windows version.