https://learn.microsoft.com/en-us/windows/apps/
https://learn.microsoft.com/en-us/windows/apps/get-started/s...
https://learn.microsoft.com/en-us/windows/win32/api/
It covers near everything, is extremely exhaustive, and constantly updated. That being said, if you're more interested in how the Windows API is organized/works internally (why you have to give it handles/resources and what those mean, for instance), then Charles Petzold's series is generally considered the definitive resource: