Here is the store description:
Ubuntu on Windows allows one to use Ubuntu Terminal and run Ubuntu command line utilities including bash, ssh, git, apt and many more.
To use this feature, one first needs to use "Turn Windows features on or off" and select "Windows Subsystem for Linux", click OK, reboot, and use this app.
The above step can also be performed using Administrator PowerShell prompt: Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-Subsystem-Linux
After above is done simply use "ubuntu" command in cmd.exe or launch Ubuntu from the start menu.
Users will be able to run Linux and Windows apps on their PC without needing to dual-boot both. While Release Preview users can't take full advantage of the Ubuntu app until the Windows 10 Fall Creators Update coming later in the year, those in the Windows Insider program should be able to play with it at full capacity.