Introduced last June, it will be a free upgrade for Windows 10 users.
Beyond the interface changes, Windows 11 will integrate several interesting features for PC gamers: AutoHDR like on Xbox consoles, the DirectStorage API (which will improve loading times on computers with SSD and NVME drives) and improved integration with Xbox Game Pass through the Xbox app.
The official date is 5 October, although the arrival on individual PCs will be staggered; it is expected to arrive gradually until mid-2022. PCs with Windows 11 pre-installed will go on sale on the 5th itself.
Some features will not be available on that day. For example, Windows 11 will run Android apps through the Amazon App Store thanks to Intel Bridge, but this will come later.