is an automated, "All-In-One" (AIO) batch script used to activate Microsoft products, specifically Windows and Office. The number 46 refers to the specific version or update iteration of the script.
Version 46 of the script is popular because it includes several refinements over older releases: kms-vl-all-aio-46
To understand the script, you have to understand the technology it mimics: is an automated, "All-In-One" (AIO) batch script used