Microsoft released upon the world a technical preview of Windows 10 and even though Cortana does not work in this version, there are still assets related to the feature in the build. Because of this, you can crack open these files and take a look at what is coming down the pipe for the platform.
The new feature uses geo-fencing to determine when to turn off or on your Wi-Fi. For example, when you come home from work, Cortana will know to turn your Wi-Fi on to connect to your network. Likewise, when you leave, it will turn off Wi-Fi but say you go to your friends house who has Wi-Fi, Cortana will know to turn it back on thanks to geo-fencing.