Windows 10 IoT Core is a new edition of Windows that is designed specifically for small embedded devices such as the Rasberry Pi 2 and Intel MinnowBoard Max. Based on Windows 10, IoT core can run Universal Windows apps written in Vistual Studio 2015 with languages like C++, C#, JS, VB, Node.js and Python. If your embedded device has the ability to connect to a display, you can create rich experiences similar to full screen apps on a Windows 10 PC. Best of all, Windows 10 IoT Core is free!
In the final release, Microsoft has included support for Bluetooth and WiFi radios which is a very welcome addition so makers can finally untether their devices that were previously required to leverage Ethernet for network connectivity. Take a look at the release notes for a full list of changes and known issues.
To get an idea of what is possible with Windows 10 IoT, check out the Microsoft hackster.io site where fellow makers share their Windows IoT creations.
Windows 10 IoT robot picture from Rover project on hackster.io