It starts with Microsoft Copilot but there are over 150 new features as well as new Surface devices. See the announcement at Announcing Microsoft Copilot, your everyday AI companion (https://blogs.microsoft.com/blog/2023/09/21/announcing-microsoft-copilot-your-everyday-ai-companion/) as well as a list of Windows September top features highlights (https://news.microsoft.com/wp-content/uploads/prod/sites/664/2023/09/FINAL_September-Continuous-Innovation-Update-Top-Features-Highlights_general_permissions-1.pdf).
You can also watch the video of the presentation at https://www.microsoft.com/en-us/event (https://www.microsoft.com/en-us/event).