Every 90 days a request is made to the KMS server by your installed Microsoft products, so it is important for Microsoft Toolkit to be continually running as a service on your machine to answer these requests.
Microsoft Toolkit mimiks this technology by creating an emulated instance of a KMS server on your machine, answering the activation requests of your Windows / Office installation by providing it with a pre-generated volume license key. “KMS” (Key Management Service) is a technology developed by Microsoft that provides large corporations with the ability to license products such as Windows and Office in bulk. Microsoft Toolkit was created to allow easy activation of all Microsoft Windows (Windows 10, Windows 8.1, Windows 8, Windows 7) and Microsoft Office (Office 2003, Office 2007, Office 2010, Office 2013, Office 2016) products via a process called KMS.
Microsoft Toolkit 2.6.6 (also know as EZ-Activator) is a set of tools created by CODYQX4, and originally made available via the forums.