It stands for Long Term Servicing Branch, I don't think it's available to the general public. You can only get it if you have a volume license agreement with Microsoft.
Blurb
Long-term Servicing Branch Specialized systems—such as PCs that control medical equipment, point-of-sale systems, and ATMs—often require a longer servicing option because of their purpose. These devices typically perform a single important task and don’t need feature updates as frequently as other devices in the organization. It’s more important that these devices be kept as stable and secure as possible than up to date with user interface changes. The LTSB servicing model prevents Windows 10 Enterprise LTSB devices from receiving the usual feature updates and provides only quality updates to ensure that device security stays up to date. With this in mind, quality updates are still immediately available to Windows 10 Enterprise LTSB clients, but customers can choose to defer them by using one of the servicing tools mentioned in the section Servicing tools.
Note LTSB is not intended for deployment on most or all the PCs in an organization; it should be used only for special-purpose devices. As a general guideline, a PC with Microsoft Office installed is a general-purpose device, typically used by an information worker, and therefore it is better suited for the CB or CBB servicing branch.
Microsoft never publishes feature updates through Windows Update on devices that run Windows 10 Enterprise LTSB. Instead, it typically offers new LTSB releases every 2–3 years, and organizations can choose to install them as in-place upgrades or even skip releases over a 10-year life cycle.
Note Windows 10 LTSB will support the currently released silicon at the time of release of the LTSB. As future silicon generations are released, support will be created through future Windows 10 LTSB releases that customers can deploy for those systems. For more information, see Supporting the latest processor and chipsets on Windows in
Lifecycle support policy FAQ - Windows Products.
LTSB is available only in the Windows 10 Enterprise LTSB edition. This build of Windows doesn’t contain many in-box applications, such as Microsoft Edge, Windows Store client, Cortana (limited search capabilities remain available), Microsoft Mail, Calendar, OneNote, Weather, News, Sports, Money, Photos, Camera, Music, and Clock. Therefore, it’s important to remember that Microsoft has positioned the LTSB model primarily for specialized devices.
Note If an organization has devices currently running Windows 10 Enterprise LTSB that it would like to change to the CB or CBB servicing branch, it can make the change without losing user data. Because LTSB is its own SKU, however, an upgrade is required from Windows 10 Enterprise LTSB to Windows 10 Enterprise, which supports CB and CBB.
