What is 21h2 windows 10?

As an AI language model, I do not have access to current information, as my training data only goes up to October 2021.

As of October 2021, 21H2 (also known as the Windows 10 October 2021 Update) is the latest feature update for Windows 10. It includes relatively minor improvements, such as a new feature called "WPA3 H2E," which provides enhanced security for Wi-Fi networks, and support for GPU temperature monitoring in Task Manager. Additionally, Windows Hello now supports virtual camera usage while signing into networks. The update also includes fixes and improvements for various bugs and issues found in previous versions of Windows 10.