SSH is Secure Shell -- the standard way to login to a remote system and execute commands, administer systems, and generally communicate. It's the fundamental access and control mechanism for most of the internet. Windows has been a holdout for decades because Microsoft wants you to use their GUI and that's all. Even Apple has had SSH on its OS X computers from the very beginning, and it's a useful and very common service on Macs.
Microsoft's arrogant and petulant attitude has hampered the acceptance and use of Windows in heterogeneous computing environments, and made work life hell for engineers, testers, and system admins.
Those of us who have had to use Windows in development work environments where SSH is the communications standard have had to install third-party products, notably Cygwin and similar utility packages, to bring OpenSSH to our Windows machines.
So for Microsoft to allow Windows to, at last, support a native OpenSSH service is a breath of fresh air like no other.