FAQ: Windows 10 LTSB explained
Windows 10 powered to its third anniversary this year, but one branch, identified by the initials L-T-S-B, remained an enigma to most corporate users.
LTSB, which stands for "Long-term Servicing Branch," was among the pillars of Windows 10 in the months leading up to, and for months after, the mid-2015 roll-out of the operating system. For a time, it seemed that it had a shot at becoming the Windows 10 for enterprise because it was seen as a calm port in a storm of radical change.
That hasn't happened, in part because Microsoft has steered customers away from LTSB.