We began hearing rumors about Windows 10 Cloud a month ago. Similar to Windows RT, it will only allow users to download apps from the Windows Store, albeit with an option to upgrade to Windows 10 Pro. When build 15025 of the OS leaked, however, Project Centennial apps - apps that were converted from Win32 for the Store - weren't supported, despite screenshots from build 15019 that indicated otherwise.
In a newly leaked build, those Win32 apps are indeed supported, which means that you'll be able to download and run apps like Slack and Evernote. Unfortunately, you still can't download Win32 apps from the Internet, such as Google Chrome; as expected, you're limited to what's in the Windows Store.
There are still a bunch of system apps that you can't run, such as the Command Line and the Registry Editor. OneDrive integration doesn't work either, as that's a Win32 app.
Some of the messages that tell you that you can't install Win32 apps have changed as well. For example, when you attempt to install Chrome, Windows 10 Cloud will now tell you about why Edge is a better browser, rather than simply telling you that you're trying to run something that's not supported.
Source: Windows Central