With Linux command line called Bash it's possible to type in those familiar Linux commands and run CLI (= Command Line Interface) apps. In addition, you can reach your Windows files by mounting NTFS partitions.
So far there has been two solutions around if you wanted to run Linux on top of Windows; virtual machine (Virtualbox, VMware) or Cygwin. However, Microsoft's approach is somewhat different and Linux command line is tied closer to Windows 10.
The company which is co-operating with Microsoft is London based Canonical Ltd - the one behind Ubuntu Linux.
For us ordinary users bringing Linux command line on Linux might not sound very attractive. Why should I use it? There is already a command line similar to Microsoft DOS inside Windows and is hardly ever used. Microsoft is aiming at developers which benefit from tools they are used to work with. The rest of us - what difference does it make?
By adding Bash Microsoft promises anyone familiar with commands like apt-get can install and run Linux apps on Windows 10. However, X Window System is a no-go. An app which needs GUI is not on supported. This is why Bash on Windows 10 will benefit only developers.
Ubuntu Linux CLI