1. This is a solution to be noticed by developers of add-ins or languages leveraging Visual Studio,
2. It has two variants: the "integrated" and "isolated" modes. If you build tools or languages that run within Visual Studio standard editions, then "Integrated" mode is your mode. If you wish to create a solution that leverages the core features of Visual Studio but isn't branded as Visual Studio, then "isolated" is your mode.
3. In Isolated mode, end-users of our product are not required to have Visual Studio on their machines, with Integrated mode they are.

Therefore it's a framework for building applications that integrate into Visual Studio or use the core feel of Visual Studio as a foundation for an entirely new and unrelated product. Definitely something worth checking out if you have an interest or commitment in developer tools. Have a look here..