Mindstorms is a product that was developed by the LEGO® company in Denmark in collaboration with the Media lab from the Massachusetts Institute of Technology (MIT). In this collaboration MIT delivers the educational ideas and LEGO performs them by expanding their products.
This is an initiative to make the Mindstorms EV3 accessible for other programming languages. ~ is a Debian Linux especially tailored for the EV3 brick. You burn it on a microSD card and boot the EV3 from that card. It then runs a Debian Linux (Jessie) which you can access with ssh (for example).
Python on ev3dev