https://www.ghacks.net/2023/10/03/windows-copilots-is-showing-third-party-ads-to-windows-users/ :
Windows users who have installed the preview update may see advertisement when they interact with Copilot. Asking Copilot for the best gaming laptops returns five suggestions, similar to what Bing Chat would provide, and ads at the end of the output.

Not all interactions with Windows Copilot may return content and ads, but some do. The entire feature requires a constant Internet connection. Even Windows-specific tasks, such as turning on Dark Mode, require Internet.

Microsoft has started to push advertisement in various locations in Windows, for instance in the Start Menu, Get Help app, or the Settings app. Most of the ads are for Microsoft products, some free, like Microsoft Edge, or subscription-based, such as Microsoft 365. The ads that Windows Copilot displays may promote third-party products and services.