Microsoft's Windows 10X operating system is mostly focused on UWP and web apps, but Microsoft understands that Win32 is essential for many users, so when the OS was announced, it was said that it would run Win32 apps in a container. Thanks to a leaked video shared by Twitter user The Walking Cat (via ZDNet), we get to see an explanation of how containerized apps work ahead of time.
For Win32 apps, Microsoft will be using a container similar to the Windows Subsystem for Linux, and every Win32 app will run on the same container, and almost every Win32 app is supported by the container. Because apps are containerized, they can't make changes to system files or the registry, so certain apps may have an issue with that. Most specifically though, that means drivers can't be manually installed through executable files, for instance.
Win32 apps will still be relatively easy to use on Windows 10X, though, because certain things are shared with the host OS. The folder and path structure is the same you'd expect, and user files are shared across the host and the container, but private app data isn't. Common hardware, like the keyboard, mouse, graphics, audio, and more have a "fast path" to the host, so they'll work as normal. Privacy-sensitive hardware like webcams and microphones will be enabled at the user's discretion, but this works at the container level, so if you allow access to a Win32 app, every Win32 app can access that hardware.
Microsoft also talked about the system tray, which is no longer a part of Windows 10X. That means you won't see some of the icons you may be used to seeing, but Microsoft says it hasn't removed the APIs for system tray icons, so the apps that try to use it won't crash or run into issues – you simply won't see those icons.
Then there are, of course, MSIX and Native containers, which already exist. These offer a more robust installation and uninstallation experience and have higher trust levels than the Win32 containers. The native container also naturally offers the best performance of all three. The MSIX container apps also run inside the general Win32 container.